MATH 120 Chapter 1-4 – Flashcards
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What is a qualitative variable
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variables that allow for classification of individuals based on some attribute or characteristic
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what is a quantitative variable
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variables that provide numerical measures of individuals.
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what variable can be added or subtracted to provide meaningful results?
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quantitative
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What is a discrete variable
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a quantitative variable that has either a finite number of possible values or a countable number of values
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what is a continuous variable
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a quantitative variable that has infinite number of possible values that are not countable
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a variable is at the nominal level of measurement if
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the values of the variable name, label, or categorize. can not be arranged in a ranked or specific order
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a variable is at the ordinal level of measurement if
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it has the properties of the nominal level of measurement but it can be arranged in a ranked or specific order
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a variable is at the interval level of measurement if
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it has properties of the ordinal level of measurement and the difference in the values of the variable have meaning. addition and subtraction can be performed
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a variable is at the ratio level of measurement if
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it has the properties of the interval level of measurement and the ratios of the value of the variable have meaning. a value of zero means the absent of quantity. multiplication and division can be performed
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what is random sampling
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the process of using chance "randomness" to select individuals from a population to be included in the sample
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how is a simple random sample obtained?
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a sample size of n from a population of N
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what is simple random sampling
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if every possible sample of size n has an equally likely chance of occuring
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how do you obtain a simple random sample in statcrunch
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data > simulate data > discrete uniform > sample size goes in random > population size goes in Maximum
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how is a stratified sample obtained
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by separating the population into non overlapping groups called strata and then obtaining a simple random sample from each stratum
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true or false ? the individuals within each stratum of a stratified sample should be alike in some what
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true
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how is a systemic sample obtained
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by selecting every kth individual from the population
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true or false the first individual selected within a systemic sample corresponds to a random number between 1 and kth
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true
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how is a cluster sample obtained
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by dividing the population into groups and selecting all individuals from within a random sample of the groups.
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how is a stratified sample obtained
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by dividing the population into homogeneous groups and randomly selecting individuals from each group.
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how do you obtain relative frequency
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rF= Frequency / sum of all frequencies
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how to obtain relative frequency in statcrunch from RAW data
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open statcrunch > type in all your numbers > select stat > tables > frequency > compute
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how do you create a bar chart in statcrunch
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graph > bar plot > with summary
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how do you create a pie chart in statcrunch
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graph > pie chart > with summary
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in a relative frequency distribution, what should a relative frequency add up to
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1
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what is a bar graph
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a horizontal or vertical representation of the frequency or relative frequency of the categories. The height of each rectangle represents the category's frequency or relative frequency.
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what is a pareto chart
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bar graph whose bars are drawn in decreasing order of frequency or relative frequency.
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Why is the median resistant, but the mean is not
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The mean is not resistant because when data are skewed, there are extreme values in the tail, which tend to pull the mean in the direction of the tail. The median is resistant because the median of a variable is the value that lies in the middle of the data when arranged in ascending order and does not depend on the extreme values of the data
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how do you determine the sample mean pulse
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add all the numbers up within the sample and divide by the amount of items listed in the sample . a-10 b-20 c-30 add abc and divide by 3
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what is sensitive to extreme values
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the mean
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what is not sensitive to extreme values
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the median
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what is considered resistant
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the median bc its not resistant to extreme values
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if a distribution is skewed left what does the mean tend to be larger or smaller than the media
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smaller than the median
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if a distribution is skewed right does it increase the value of the mean
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yes
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true or false, with symmetric distributions the mean and median are close in value
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true
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when a data set is skewed what is the preferred tenency
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the median
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what is the mode
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the most frequent observation that occurs
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what is dispersion
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the degree to which the data are spread out
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true or false, when comparing 2 populations, the larger the standard deviation, the more dispersion the distribution has, provided that the variable of interest from the 2 populations has the same unit of measure
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true, because the standard deviation describes how far, on average each observation is from the typical value. a larger Standard deviation means that observations are more distant from the typical value, and therefore are more dispersed
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how to you find population variance in statcrunch
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click on unadj. variance
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how do you find the population standard deviation in statcrunch
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click on unadj standard deviation
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how do you find sample variance in statcrunch
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click on variance
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how do you find the sample standard deviation in statcrunch
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click on standard deviation
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in order to use the empirical rule what must a histogram be
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roughly bell shaped
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what is the empirical rule
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for a normal distribution nearly all the data will fall with in 3 standard deviations of the mean 68% , 95%, or 99.7%
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what makes a range less desirable than the standard deviation as a measure of dispersion
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the range does not use all the observations where as the standard deviation uses all the observations
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what is range
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the difference between the largest data value set and the smallest data value set
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what is a z score
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represents the distance that a data value is from the mean in terms of the number of standard deviations
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what do quartiles do
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divides the data sets into 4ths
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how do you find z scores
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value - mean divided by standard deviations
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if a z score is postive where will it be in relation to the mean
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above
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if a z score is negative where will it be in relation to the mean
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below
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what is an outlier
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if a data value is smaller than a lower fence or greater than an upper fence the value is an outlier
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how do you find Q1, Q2, and Q3 in statcrunch
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click on Q1, Q3 and median
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how do you check for outliers in a data set
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sort the numbers in statcrunch and see which numbers are below the lower fence or above the upper fence
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how do you find a 5 number summary in stat crunch
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click min, max, median, Q1, and Q3 > compute> then arrange in accending order
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what is a response variable
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variable whose value can be explained by the value of the explanatory variable
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what is the explanatory variable
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the predictor variable
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what is a scatter diagram
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a graph that shows the relationship between 2 quantitative variables measured on the same individual. Each individual is represented by a point on the diagram. The explanatory variable is plotted on the horizontal axis and the response is on the vertical
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what does it mean if 2 variables that are linearly related
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they are positively associated
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true or false, if one value increases so does the other value
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true
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true or false, if it is negatively associated one value will decrease the other will increase
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true
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what is a linear correlation coefficient/Pearson product moment correlation coefficient
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measure of the strength and direction of the linear relation between 2 quantitative variables
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what does it mean if r = +1
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then a perfect positive linear relationship exist
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what does it mean if r= -1
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then a perfect negative linear relationship exist
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what does it mean if r is close to zero
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then little to no evidence exists
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since the correlation is not resistant what happens
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the observation that does not follow the overall pattern of the data could affect the value of the linear correlation coefficient
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how do you fine the linear correlation coefficient in statcrunch
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stats > summ stats > correlation
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what is residual
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the distance between the observed and predicted values of y is the error
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what is least squares regressionline
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the line that minimizes the sum of the squared errors or residuals
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What is the difference between a bar chart and a histogram
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the bars on a bar chart do not touch while the bars of a histogram do touch.
