Relationships between two variables
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The simplest level of measurment is
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Nominal
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If people are classified as either literate, semi-literate, or or illiterate, measurement is
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Ordinal
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Ranked data are associated with
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Ordinal measurment
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Six is twice three only when these numbers emerge from a scale of measurment having
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A true zero
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To determine wheather a new sleeping pill is effective, adult insomniacs recieve a pill (either real or fake, according to some impartial assignment rule) and subsequently their sleeping times are measured, in minutes, during eight-hour observation periods. In thisnstudy, sleeping time is
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The dependent variable
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When variables cannot be manipulated by the investigator, relationships must be studied with
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Observational studies
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In a frequency distribution for grouped data, the leftmost column consists of
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Class intervals
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Whenever an outlier is encouraged, first attempt to
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Verify its accuracy
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Frequency distributions for qualitative data are relatively easy to constuct because
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Classes or categories are dictated by the data
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A frequency polygon is
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A line graph
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If the incomes of equal numbers of skilled and unskilled wage earners appear in a single distributiom, the resulting frequency distribution probably will be
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Bimodal
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The feature that idstinguishes bar graphs from histograms is the use of
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Gaps between bars
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A frequency distribution of scores on a very difficult statistics test probably will be
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Positively skewed
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If you wish to graph the distribution of times spent dreaming during sleep (as inferred from rapid eye movement) for a sample of young adults, use
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A histogram or frequency polygon
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For the following observations: 2, 5,3,2,4,6,2,4, the mode equals
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2
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The identification of the median becomes increasingly cumbersome with larger sets of unorganized data because
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Data must be irdered from least to most
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Which one of the following is true of the mean
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Equals the sum of all observations divided by the number of observations
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In the formula for the sample mean (or for the populations mean) the symbol £ represents
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The operation of summing all observations
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The symbol for the pupolation mean is
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Mu
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If qualitative data can be ordered, its possible to use
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The mode or median
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The sum of the deviations of all observations about the mean equaks
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Zero
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The distribution of annual incomes for US households is positively skewed. If the cencus reports a median annual income of $57,450, this implies that the mean annual income is
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Larger
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Whcihc average, the mode, median, or mean, probably serves as the basis for the following statement? The average college professor is a white man
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Mode
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An attractive featyre of the range is that it
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Can be easily understood
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If a survey of a grade school children reveals that the distribution of the daily tv viewing times has a mean of 2.3 hours and a standard deviation of 1.0 hours, this implies that
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A majority of children watch tv between 1.3 and 3.3 hours
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Compared to the standard deviation for the distribution of salaries fro all new college graduates, the standard deviation for then distribution of salaries for all new electrical engineers should be
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Smaller
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The interquartile range often is used with the
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Median
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If a set of scores approximates a normal curve, scores having intermediate values will be
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Most prevalent
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On a reding comprehension test, it would be preferable to acheive a z score of
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2.34
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Since the normal curve is an idealized curve that is presumed to describe complete sets of populations, the mean and standard deviation of the normal curve are respresented by the symbols
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Mu and Q, respectively
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A negative z score signifies that the orginal score is
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Below the mean
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The total area under the normal curve always equals
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1.0000
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When solving normal curve problems that involve two z scores
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Enter the tables twice, once for each z score
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Given that IQs are normally distributed with a mean of 100 and a standard deviation of 15, what proportion of IQs are above 115?
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.16
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Given that IQs are normally distributed with a mean of 100 and a SD of 15, what proportion of IQs fall between 130-145?
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.02
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Distributions of z scores can be obtained from ____ distribution of orginsl scores
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Any
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If kristen earned z scors of 2.50, 1.00, and -0.50 on her final exams in statistics, literature, and philosophy, respectively, she preformed most poorly in
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Philosophy
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If a positively skewed distribution of incomes is transformed into a distribution of z scores, the shape of the new distribution will be
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Positively skewed
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If you were attempting to take a random sample from a real population consisting of 6,000 people, you would use random numbers having
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Four digits
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Assume that in a statistics class the probability of recieving a grade of A equals .30 and the probability of recieving a grade of B equals .30. The probability that a randomly selected student from this class will recieve a grade other than an A or B equals
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.40
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You might choose to survey an entire population if the population is
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Small
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Pollsters conduct surveys based on
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Real populations
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Probability refers to the
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Proportion of times some event will occur
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To obtain an exact replica of a population, take a
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Complete survey of the population
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The sampling distribution of the mean describes
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All sample means that could occur just be chance
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Greek letters are used to describe characteristics of
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Sampling distributions and populations
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The standard error of the mean serves as a rough indicator of the average amount by which sample means deviate from
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The population mean
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Given that the population SD equals 40 and that the sample consists of 25 observations, the standard error of thr ,eam equals
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8
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A random sample of 100 college students is taken from the student body of a large university assume that, in fact, a population SD of 15 describes the weekly student estimates for the entire student body. Therefore, the sampling distribution of the mean has a Standard error that is
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Equal to 1.50 hours
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A random sample of 100 college students is taken from the student body of a large university assume that, in fact, a population mean of 20 hours and a population SD of 15 hours describe the weekly study estimates for the entire student body. About 95 percent of the sample means in this sampling distribution should be between approximately
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17 and 23 hours
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A rare outcome signifies that, with respect to the null hypothesis,
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Something special is happening in the underlying population
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If the sampling distribution of X bar is normally distributed, then, it would be most informative to describe the corresponding sampling distribution for Z as
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The standard normal distribution
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To express a sample mean as a Z ratio,
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Subtract the hypothesized population mean and divide by the standard error
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In the step by step hypothesis testing procedure, the first step describes the
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Research problem
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One very prevalent decision rule specifies that the null hypothesis should be rejected if the observed Z
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Equals or is more positive than 1.96 or equals or is more negative than -1.96
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Insofar as we must generalize from a sample to a population, the observed difference between the sample mean and the hypothesis population mean
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Is described by all of the above
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An investigator is concerned only about directing the possibility that the mean IQ for a pupation of high school students is smaller than 100. Therefor, the alternative hypothesis should take the form
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Mu<100
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It doesn't make sense to test a null hypothesis that the population mean equals the observed value of the snake mean because
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The Z ratio always would equal zerp
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If the null hypothesis is really false and we reject the hypothesis, we have made a
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Correct decision
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Given an observed difference between a sample mean of 42 and a hypothesized population mean of 50, you
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Must determine whether this observed difference can reasonably be attributed to chance
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The 0.05 level of significance indicates a degree of rarity of one time in
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Twenty or less
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The probability of a type II error equals
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Beta
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The smallest overlap between true and hypothesized sampling distributions would occur when the effect is
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Very large
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Generally speaking, a larger level of confidence should be reserved for those situations where
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A false interval has serious consequences
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Specify which one of the following 95 percent confidence intervals would be most preferable, given that you wish to demonstrate that a summer workshop increases GPAs
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2.90-3.40
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Compared to the normal distribution, a distinctive property of the t distribution is its
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Inflated tails
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Confidence intervals for the population mean specify
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A range of values that includes the population mean with a known degree of confidence
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If the desired number of degrees of freedom doesn't appear in the t table, use the critical t associated with
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The next smallest df in the table
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To obtain the estimate standard error, divide the sample standard deviation by
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Square root of n
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Given that three gas mileage tests yield a mean of 30 miles per gallon, and that two of these tests have values of 27 and 29, the third test must have a value of
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34
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In a study with 30 grade school children per group, students in then experimental reading program do 10 points better, on average than do students in the regular program. Thereof you can conclude that this difference is
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Undecipherable without additional information
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If daily meditation has little or no effect on college grade point average, the difference between population means is
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Close to zero
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A researcher would prefer to report an approximate p value that is
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Less than 0.01
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The importance of a statistically significant result might be clarified with
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All of the above
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The t test for two independent samples assumes that both underlying populations are normally distributed with equal variances. You needn't be too concerned about violations of the assumptions of t for two independent samples (normally distributed populations with equal variances) as long as both samples sizes are
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Equal and family large
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Cohen's D is
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All of the above
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Which one of the following does not illustrate two related samples
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College freshmen are split into two groups
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If two related samples each consists of 15 subjects, a 99 percent confidence interval will be based on degrees of freedom equal to
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14
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Cohen's guidelines for values of D associated with small, medium, and large effects are
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Are the same regardless of whether the two samples are independent or related.
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When subjects perform double duty in both conditions of an experiment, the order in which conditions are experienced should be
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Counterbalanced
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The dream times for each of twenty volunteers are measured during two sleep periods: once after an evening when no alcohol was consumed and once after an evening when alcohol was consumed. It would be appropriate to test the null hypothesis which a
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Two tailed test at the .05 level of significance
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A medical researcher compares the blood pressure readings for a group of high risk patients both before and after the administration of a new tension reducing drug. The appropriate test would be a
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t test for two related samples
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The sample sizes for two related samples must be
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Equal
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If a treatment effect exists
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Variability between groups will tend to exceed variability within groups
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Is the null hypothesis is false, variability between groups refleqcts
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Both random error and the treatment effect
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Regardless of whether the null hypothesis is true or false, variability within groups reflects
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Only random error
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If th null hypothesis is false because of a sizable treatment effect, the value of F tends to be
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Considerably larger than one
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In analysis of variance, variance estimates consist of
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Sum of squares divided by degrees of freedom
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In analysis of variance, vRiance estimates often are referred to as
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Mean squares
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In an experiment involving three different groups, each consisting of 10 subjects, the degrees of freedom for within groups equals
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27
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In a table that summarizes the results of an analysis of variance, the word \"between\" might be replaced by
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Treatment
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Rejection of the overall null hypothesis usually raises some additional questions regarding
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Both a and b
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When all possible differences between pairs of population means are evaluated not with an F test, but with a series of regular t tests, the probability of at least one
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Type I error is larger than the specified level of significance
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Tukeys test should be used only if
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The overall null hypothesis is rejected
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Tukeys HSD controls the
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Cumulative Probability of a type I errors.
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In Those cases where the status of a particular comparison is ambiguous, being designated as significant by some multiple comparison tests and as no significant by the remaining tests, it is suggested that this comparison be reported as having
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Borderline significance
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Use Cohen's D to estimate the effect size of
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Any significant difference between pairs of means
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If a published report of an F test specified that p<O.01, you could conclude that the test result is
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Rare, supporting the research hypothesis
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You needn't be too concerned about violating the assumptions of the F test so long as
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Sample sizes are equal and larger than 10
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Without doing any calculations, describe the relationship for the following pairs of observations
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Negative
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Which one of the following most likely describes a positive relationship
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Years of education and lifetime earnings
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Scatterplots
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All of the above
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For the relationships between caloric intake and weight gain, the dot cluster should show
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A tilt for the lower left to the upper right
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Given that the relationship between GPA and IQ is stronger in high school than in college, the dot cluster for high school (compared to that for college) should
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More closely approximate a straight line
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Which one of the following relationships is perfect?
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Heights of adults, each describes twice-once in inches and once in centemeters
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Which one of the following numbers couldn't possibly be a value of r?
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1.03
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If everyone paid taxes equal to 10 percent of their total annual income, the value of r for income and taxes would be nearest to
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1.00
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The z score formula for r
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Has all of the above properties
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Although designed originally for the use with quantitative data, the Pearson r has been entrenched to other kinds a of situations, including those that involve
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All of the above
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Dots in scatter plots that deviate conspicuously from the main dot cluster are viewed as
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Potential outliers
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When outliers occur, the best strategy is to report
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The value of r both with and without any outliers
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Big table on test 3. After duplicate correlations have been discarded and trivial correlations have been ignored
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Three correlations
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Big table on test 3. Only ___ of these correlations should be taken seriously
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Two
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There is a negative correlation between years of heavy smoking and life expectancy. Therefore, for someone who has smoked heavily for many years,myou would predict a life expectancy that us
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Relatively short
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When using a scatter plot, the customary direction of predictions from
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X to Y
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In a scatter plot, predictive errors are associated with
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Vertical discrepancies between dots and the regression line
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Given Y'=0.005(X)+0.40 for predicting college GPA for SAT critical reading scores, the predicted GPA for a student with a SAT score of 600 would be
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3.40
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A student concentrating of raising his SAT score in order to raise his college GPA. This strategy is questionable because it assumes that the relationship between SAT scores and college GPA is
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Cause-effect
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A predicted college GPA is unlikely to coincide with a students true GPA because the relationship between SAT score and college PGA is
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Imoerfect
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The least squares regression equation minimizes
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The total of all squared predictive errors
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If a least squares equation predicts annual income from years of education, as a college student you would prefer that the value of b, the slope of the equation, equal
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1.6
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Which one of the following numbers would be preferable for the standard error of estimate?
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20
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Before attempting to predict performance of a high stress job from anxiety scores, you should first establish that the underlying correlation is
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Strong
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Use of the standard error of estimate assumes that
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The underlying relationship is linear
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Assume that the equation for predicting the rate of inflation from the percent of unemployed workers is as follows: Y,= -0.90(X)+ 11 If the unemployment rate equals 10 percent, the inflation rate should equal
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2 percent
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The regression fallacy is committed whenever regression toward the mean is interpreted as an effect that is
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Real
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