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1st Quartile*

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25th percentile of the observation below it

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2nd Quartile

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50th percentile of a data set, the Median

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3rd Quartile

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75th percentiles of a data set

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68-95-99.7 Rule*

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In all score-based normal curves, 50% of the scores fall at or above the mean and 50% at or below the mean. (Approximately 68% of all scores fall within one standard deviation of the mean, 95% within two standard deviations, and 99.7% within three standard deviations)

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Actual Sample*

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Part of the population from which we actually collect information

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Alpha

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Known as SIZE or TYPE-1 ERROR. Type 1 Error: isn't fine but found out was Fine, error that doesn't cost lives

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Bar Graph*

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Graph of the distribution of a categorical variable; can compare any set of quantities measured in the same unitused with the categorical data to compare the sizes of categories.

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Bias*

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If the design of a statistical study symmetrically favors certain outcomes

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BoxPlot*

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Based on the 5-number summary of a data set. Each value in the 5-number summary is located over its corresponding value on a number line.

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Categorical Variable (qualitative)

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Any variable that is not quantitative is categorical. Categorical variables have no numerical meaning. Examples: Hair color, gender, field of study

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Chi-square*

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Method for testing the association between the row and column variables in a two-way table. Used to determine whether there is a significant difference between the expected frequencies and the observed frequencies in one or more categories.

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Coefficient of Determination

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Assess how well a model explains and predicts future outcomes

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Complement*

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Is the opposite of the probability of something happening. of an event is the event not occurring.Given the probability of an event, the probability of its complement can be found by subtracting the given probability from 1. The set of all outcomes in the sample space that are not included in the outcomes of event A.

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Control Group*

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A group that does not receive the treatment

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Convenience Sample*

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A sample where the subject are selected, in part or in whole, at the ease of the researcher. A statistical method of drawing representative data by selecting people because of the ease of their volunteering or selecting units b/c of their availability or easy access.

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Correlation*

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Measure the direction and strength of the linear association between two quantitative variable (x and y) Possible correlations range from +1 to -1. A zero correlation indicates that there is no relationship between the variables. A correlation of -1 indicates a perfect negative correlation, meaning that as one variable goes up, the other goes down. A correlation of +1 indicates a perfect positive correlation, meaning that both variables move in the same direction together

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Cut Point for Outliers

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The conventional cut-off point is 4/n

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Disjoint*

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When two events share no common outcomes. To separate or disconnect the joints or joining of; no outcomes

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Double Blind*

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Neither the experimenters nor the participants know which participants are in the experimental and control groups.

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Exhaustive

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When a set of events comprises all possible occurrences of a reference set

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Expected Value

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The counts we would expect -except for random variation-if the H0 were true

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Experiment*

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imposes some treatment on individuals in order to observe their responses

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Explanatory variable*

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x-value Variable that explains or causes changes in the response variable. The independent x variable

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Form, Direction, Strength, outlier*

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Form, Direction, Strength, outlier are information that describes Scatterplots Form - If there is a straight line (linear) relationship, it will appear as a cloud or swarm of points stretched out in a generally consistent, straight form Direction- Positive or negative association on graph, Strength - How close the points in the scatterplot lie to a simple form such as a line. Outlier - is an observation that lies an abnormal distance from other values in a random sample from a population, points that do not follow the pattern.

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Histogram*

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a graph that shows quantitative numbers where the bar touches. Shows how frequently data occur within certain ranges or intervals. The height of each bar gives the frequency in the respective interval.

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Independent*

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There is a no relationship between the two categorical variables that is in the rows

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Interquartile range

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distance between the first and third quartiles, aka the distance between the 75th percentile and the 25th percentile.

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Matched Pairs

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The design of an experiment for paired comparison in which the assignment of subjects to treatment or control.

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Mean

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the average of a set of data (sum of values divided by # of values)

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Median

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The middle score of a distribution

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Mode*

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Most frequently occurring number

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Mutually Exclusive

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Two events cannot both cannot happen/Two events are mutually exclusive (or disjoint) if it is impossible for them to occur together.

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Negatively Associated

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A relationship in paired data in which one variable's values tend to increase when the other decreases, and vice-versa.

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Normal Distribution

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The normal (or Gaussian) distribution is a family of bell-shaped, symmetric density curve

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Non-Response Bias

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Occurs in statistical surveys if the answers of respondents differ from the potential answers of those who did not answer.

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Observational Study

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Observe individuals and measures variable of interest but does not attempt to influence the responses.

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Observed value

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Values that are given; what is seen.

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One Tailed Test

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The alternative hypothesis states that the parameter is larger than or smaller than the null hypothesis value

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Outlier

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An observation that is numerically distant from the rest of the data. an individual value that falls outside the overall pattern of the relationship

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P value

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A probability, with a value ranging from zero to one

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Parameter

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A numerical quantity measuring some aspect of a population of scores.

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Placebo

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A simulated treatment for a condition/study intended to deceive the recipient

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Population

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The entire group of individuals about which we want information from.

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Positively Associated

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When the scatter plot gives you a positive slope

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Quantitative variable

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They represent a measurable quantity

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Questionnaire Bias

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The way a question is asked to influence the response of the person

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Randomize

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Subjects are selected randomly

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Regression Line

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A straight line that describes how a response variable y changes as an explanatory variable x changes.

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Residual

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Difference between the actual and estimated function value. difference between an observed value of the response variable and the value predicted by the regression line

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Residual Plot

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Is a scatterplot of the regression residuals against the explanatory variable.

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Response Variable*

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A variable you are predicting from (dependent y value)

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Sample of Interest*

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everyone you sample and hope will respond

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ScatterPlot*

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Graph of the two quantitative variables measured on the same individuals. summary of a set of data that shows the realtionship between two variables.

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Shape, Center and Spread*

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Is the way to describe the overall pattern of a histogram.

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Simple Random Sample*

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Each individual in the population has the same chance of being chosen for the sample

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Skewed *

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A distribution is not symmetric; they are not mirror images of each other

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Skewed to the Left

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A distribution is one in which the tail is on the left side

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Skewed to the Right

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A distribution is one in which the tail is on the right side

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Square of the Correlation*r²

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It is has a value that ranges from zero to one, and is the fraction of the variance in the two variables that is shared. r², is a useful value in linear regression.

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Standard Deviation*

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Measures the spread by looking at how far the observations are from the mean; also the square root of the variance. s is zero when there is no spread and gets larger as the spread increases; square-root of the variance s squared

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Standard Normal Deviation*

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Has a mean of 0 and a standard deviation of 1

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Statistic*

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A numerical measurement describing some characteristic of a sample. The science of collecting, analyzing, and interpreting data. "Methods used to summarize, analyze, or make inferences from data" a number that can be computed from the sample data without making use of any unknown parameters

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Stratified Random Sample

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A sampling design in which the population is divided into several sub-populations, and random samples are then drawn from each stratum

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Strength*

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a scatterplot shows an association that is this if there is little scatters around the underlying relationship. how close the points in the scatterplot low to a simple form such as a line

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Treatment*

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The intervention or other controlled circumstance applied to randomly assign experimental units. Any specific experimental condition applied to the subjects

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Two-Tailed Test

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Either tail of the distribution (positive or negative) will lead to the rejection of the null hypothesis of no difference. the alternative hypothesis states that the parameter is different from the null value

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Undercoverage*

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Occurs when some groups in the population are left out of the process of choosing the sample. A bias sample in a way that gives a part of the population less representation than it has in the population.

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Variance

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The sum of squared deviations from the mean, divided by the count minus one

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Voluntary Response Bias*

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Occurs when sample members are self-selected volunteers, as in voluntary samples

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Z-Score*

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Gives the number of how many standard deviations x lies from the distribution mean. Tells how a single data point compares to normal data. Tells you not only whether a point was above or below average, but how unusual the measurement is.

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