Term
| What do covariation, covariance, and correlation measure? |
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Definition
| direction and magnitude of relationship between two variables |
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Term
| what is meant by postive versus negative relationships, zero relationship between two variables |
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Definition
| be able to make scatterplots that illustrate a perfect positive relationship, a moderate pos relationship, a zero relat, a mod neg relat, a perfect neg relat between two variables |
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Term
| What is the range of values of the Pearson product moment correlation? What are the values of teh correlation coefficient that Jacob Cohen labeled as small, moderate, and large? |
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Definition
r=.1 : Small
r=.3 : moderate
r=.5 : large |
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Term
| Correlation versus causality: what are 3 conditions required to establish causality? Does a strong correlation between two variables imply that one variable causes the other? What is meant by a "3rd variable"? a spurious relatiohsip? |
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Definition
-relationship
- control for extraneous variables
-temporal precedence : A must come before B in time |
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Term
| What are meant by curvilinear relationships? |
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Definition
| Doesn't capture the relationship |
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Term
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Definition
Categorical; the variable consists of categories only, mode, phi coefficient
EX. politcal parties, religion, etc. |
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Term
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Definition
dichotomous: variables have only 2 categories;
ex. gender, alcoholic or not alcoholic |
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Term
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Definition
| the correlation coefficient used for 2 binary variables |
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Term
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Definition
the scores reflect rank order but not equal spacing; continuous
ex, 1..2..............3.4......5 |
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Term
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Definition
the scores have equal intervals between them, but the 0 on the scale is not meaningful. continuous
ex: IQ, temperature |
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Term
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Definition
scores have equal intervals, plus a meaningful 0. continuous
ex: measures of distance/amt. |
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Term
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Definition
| SPxy = ∑ (Xi - Ẍ) (Yi - Ẏ) |
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Term
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Definition
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Term
| Pearson Product Moment Correlation |
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Definition
| rxy = SPxy/ sq.root SSx * sq.root SSy |
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Term
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Definition
SSx = ∑ (Xi - Ẍ)^2
SSy = ∑ (Yi - Ẏ)2 |
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Term
| What are the circumstances in which the Phi coeff is used? |
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Definition
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Term
| covariance for population |
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Definition
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Term
| Pearson Product moment Correlation |
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Definition
| is a relative measure that compares the covariation with the amt of variation in each variable. it is abbreviated "rho" (ρxy)in the population and "r" (rxy) in the sample. |
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Term
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Definition
| If a pair of variables has a perfect neg relat, the correlation will be minus one (-1). IF there is absolutely no relationship, the correlation will be 0. if there is a perfect pos relat, the correlation will be +1. Typically the correlation will be neither exactly 0 nor +1 or exactly -1. You might get a correlation of -.75, a strong neg relat; or a correlation of +.20, a weak pos relat; or .33, a moderate pos relat. |
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Term
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Definition
| Correlations are used to describe the strength of relationship between variables. |
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Term
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Definition
City Suburbs Total
Demo 48(A) 5 (B) 53 (K)
Repub 2(C) 45 (D) 47 (L)
50(M) 50 (N) 100 |
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Term
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Definition
| applies to nominal (categorical) variables, where both variables are binary |
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Term
| Pearson Product Moment Correlation |
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Definition
| Applies to interval and ratio scales |
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Term
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Definition
| Is the only measure of central tendency for nominal scales |
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Term
| Formula for Z SCores for individual scores in the population |
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Definition
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Term
| What is a probability distribution? |
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Definition
| a probability distribution is a distribution of proportions of areas under a curve as a funcion of X; the full area summs to 1.00. |
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Term
| In general, how does the mean of the distib. you've created relate to the population mean? |
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Definition
| The mean will be very close to the pop mean, but only once in a while will it be equal to the pop mean? |
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Term
| What is the standard deviation of the sample means called? |
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Definition
| the standard error of the mean |
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Term
| What is the symbol for the standard error of the means? |
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Definition
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Term
| What does the central limit state?L Under what circumstances do we need the central limit theorem? |
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Definition
| for samples of moderate size (say n = 25 or greater) the sampling distribution of means will be approx normally distributed, even if the pop distrubtion is skewed. You need to call upon the CLT if the variable with which you are working is not normally distributed. |
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Term
| The frequencey distribution of all the sample means is called what? |
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Definition
| the sampling distribution of the mean |
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Term
| standard error of the mean is used to mark off what? |
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Definition
| it's used to mark off the distribution |
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Term
| what does "the assumption of normality" mean? |
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Definition
| It means that the variable you are studying follows the shape of a normal distribution and that therefore the areas of the normal curve given in the normal curve table apply to the problem. What happens if you assume normality of a variable and use the normal curve to find areas, but the variable is not normally distributed. |
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Term
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Definition
| It's an unbiased estimate of the pop mean. |
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Term
| The sample standard deviation s is .... |
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Definition
| Computed with the finite sample correction (n-1) in the denominator is an unbiased estimate of the pop standard deviation. Also know that the sample mean and standard deviation estimate the pop mean and standard deviation, respectively. |
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