PY Stats 211 chapter 15

The correlation coefficient ranges between ____ and ____

-1 and +1

(#54) The correlation coefficient varies between 0 and 1 and can never be negative (T/F)?

False

(#57) A correlation of r=.50 in a sample of 15 participants is statistically significant for a two-tailed test at .05 level of significance (T/F)?

False

(#64) The assumptions of normality require that the range of scores observed in a sample is the same of the possible range of scores in the population (T/F)?

False

(#69) Restriction of range occurs when an unanticipated variable not accounted for in a research study that could be causing or associated with observed changes in one or more measured variables (T/F)?

False

(#71) The Spearman correlation coefficient is used to measure the correlation between two nominal variables (T/F)?

False

(#73) The point-biserial correlation coefficient is used to measure the correlation between two dichotomous variables (T/F)?

False

(#75) the phi correlation coefficient is used to measure the correlation between two ordinal variables (T/F)?

False

(#78) If r= 0.026 and df=10, then t=7.20 (T/F)?

False

(#42) A researcher computes the following phi correlation coefficient r (phi) = 0.42. If the sample size was 20, then what is the decision for this correlation test?

Retain the null hypothesis

(#43) A researcher determines that x^2 =3.76 to test for significance for a phi correlation coefficient. What was the decision for this phi correlation test?

Retain the null hypothesis

(#58) A correlation of r=.38 in a sample of 30 participants is statistically significant for a two-tailed test at .05 level of significance (T/F)?

True

(#65) Homoscedasticity is the assumption that there is an equal variance of data points dispersed along the regression line (T/F)?

True

(#66) Linearity is the assumption that the best way to describe a pattern of data is using a straight line (T/F)?

True

(#67) Outliers can change both the direction and strength of a correlation coefficient

True

(#68) Correlation does not show causation

True

(#70) The formula for the Spearman correlation coefficient was derived from the formula for the Pearson correlation coefficient (T/F)?

True

(#72) The formula for the point-biserial correlation coefficient was derived from the formula for the Pearson correlation coefficient (T/F?

True

(#74) The formula for the phi correlation coefficient was derived from the formula for the Pearson correlation coefficient (T/F)?

True

(#76) the correlation coefficient can be converted to a t statistic (T/F)?

True

(#77) The correlation coefficient can be converted to a chi-square statistic (T/F)?

True

The assumption that there is an equal variance or scatter of data points dispersed along the regression line is referred to as

homoscedasticity

Which of the following is the assumption that the best way to describe the pattern of data is using a straight line?

linearity

Suppose a correlation is computed in each of two samples, If the value of SSxy is the same in each sample and square root of SSxSSy is larger in sample 1, then in which sample will the value of the correlation coefficient be larger?

sample 2

The correlation coefficient is used to measure the _______ and _______ of the linear relationship between two factors

strength; direction

The normality assumption states that the population of X and Y scores form a bivariate (two variables) normal distribution, such that

-the population of X and Y scores are normally distributes -for each X score, the distribution of Y scores in normally distributes -for each Y score, the distribution of X scores is normally distributed ALL OF THE ABOVE

The numerator of the correlation coefficient measures the extent to which two variables

A-vary together B-vary independently C-covary BOTH A AND C

(#79) To summarize correlations, we report the strength, the direction, and the p value for each correlation coefficient (T/F)?

True

(#80) When we compute many correlations in a single study, we report each correlation coefficient in a table called a correlation matrix (T/F)?

True

The correlation coefficient ranged from -1.0 to +1.0 with values closer to +-1.0 indicating

a stronger relationship between two factors

The coefficient of determination is mathematically equivalent to

eta-squared

The point-biserial correlation coefficient is a measure of the direction and strength of the linear relationship between two variables, where

one is continuous, and one is dichotomous

A researcher measures the correlation in rankings for a sample of restaurants and consumers' rankings of their favorite restaurants. IF E D^2 = 96 and n = 12, then what is the value of the correlation coefficient? 0.07 0.34 0.66 0.94

0.66

Which of the following indicated the strongest correlation? r = -0.57 r = +0.78 r = -0.90 r= +0.88

r = -0.90

A researcher measures the relationship between two variables X and Y. If SSxy = 340 and SSxSSy = 320,000, then what is the value of the correlation coefficient? 0.32 0.34 0.60 almost a zero correlation

.60

A researcher measures the following correlation between number of years of education and life satisfaction r = +0.08. What is the value of the coefficient of determination? 0.08 0.16 0.01 0.11

0.01

A researcher measures the correlation of the time it takes participants to complete two tasks purported to measure the same cognitive skill. Participant times are converted to ranks from fastest to slowest. If E D^2 = 165 and n = 20, then what is the decision for this correlation test?

Reject the null hypothesis

An unanticipated variable not accounted for in a research study that could be causing or associated with observed changes in one or more measured variable is called

a confound variable

A statistical procedure used to describe the strength and direction of the linear relationship between two factors is called

a correlation

a correlation coefficient can ___ demonstrate cause

never

The correlation coefficient measures the extent to which changes in one factor are ___ in a second factor

related to changes

A researcher observes a correlation of values from 2 to 10 points and draws conclusions about the full range of values in the population from 0 to 21 points. Which limitation for correctly interpreting a correlation coefficient did the researcher violate?

restriction of range

The most common measure of effect size for the correlation coefficient is called

the coefficient of determination

the appropriate correlation coefficient for measuring the direction and strength of the linear relationship between two ranked or ordinal variables is

the spearman correlation coefficient

the coefficient of determination is

-a measure of effect size -mathematically equivalent to etq-squared -equal to the correlation coefficient squared ALL OF THE ABOVE

Which of the following is a limitation for interpreting correlation?

-correlations do not demonstrate cause-and-effect -outliers can change the direction and/or strength of the correlation -conclusions should not be drawn beyond the range of scores measured ALL OF THE ABOVE

Outliers can change the ___ of a correlation

-direction -strength -sign (+, -) ALL OF THE ABOVE

(#50) Select the description below that identifies the following correlation: r=.28, p < .01

-the correlation is positive -the correlation is statistically significant -the coefficient of determination is .08 ALL OF THE ABOVE

A researcher measures the following correlation r = -0.21, what is the value of the coefficient of determination? 0.04 -004 0.42 -0.42

0.04

If X^2 = 5.32 and n = 20, then what is the value of the coefficient of determination? 0.133 0.36 0.64 there is not enough information to answer this question

0.133

(#41) A researcher measures the correlation between the frequency of self-esteem (high, low) and health status (lean/healthy, overweight/obese). Based on the frequencies for each nominal category given below, what is the value of the phi correlation coefficient? 0.08 0.28 0.52 0.56

0.28

(#45) IF X^2 =3.84 and n=36, then what is the value of r? 0.11 0.16 0.33 0.36

0.33

(#37) A researcher measures the correlation between self-esteem (high, low) and physical fitness scores among school athletes. In the study, 12 participants reported high self-esteem, and 12 reported low. If S(r) = 9.06 and M(y1)-M(y2) = 11, then what is the value of the correlation coefficient? 0.61 0.30 0.39 not enough info

0.61

A researcher measures the relationship between narcissism and willingness to help. If SSxy = 240 and SSx = 320 and SSy = 410, then what is the value of the correlation coefficient? 0.002 0.02 0.66 0.69

0.66

the spearman rank-order correlation coefficient is a measure of the direction and strength of the linear relationship between two ___variables

ordinal

The denominator of the correlation coefficient measures the extent to which two variables

vary independently