Lectures 20-23 Quiz

Lectures 20-21 1. The scatter plot for a set of X and Y values shows the data points clustered in a nearly perfect circle. For these data, what is the most likely value for the Pearson correlation? Either positive or negative near 0 2. What would the scatter plot show for data that produce a Pearson correlation of r = +0.88? Points clustered close to a line that slopes up to the right 3. A negative correlation means that decreases in the X variable tend to be accompanied by decreases in the Y variable. False , negative correlation means X and Y are having opposite trend which indicates that as X decreases, Y will increase. 4. For which of the following Pearson correlations would the data points be clustered most closely around a straight line? -0.70 5. A researcher measures IQ and weight for a group of college students. What kind of correlation is likely to be obtained for these two variables? a correlation near zero* 6. The results from a research study indicate that adolescents who watch more violent content on television also tend to engage in more violent behavior than their peers. The correlation between amount of TV violence content and amount of violent behavior is an example of _______. A positive correlation 7. A Pearson correlation of r = –0.90 indicates that the data points are clustered close to a line that slopes down to the right. True 8. A researcher records the age and price for a group of used Hondas. What kind of correlation is likely to be obtained for these two variables? A negative correlation 9. A researcher finds a significant correlation between the amount of time spent watching television and blood pressure for a sample of 40-year-old men. This means that watching more television causes high blood pressure. False 10. Suppose the correlation between height and weight for adults is +0.40. What proportion (or percent) of the variability in weight can be explained by the relationship with height? 16% 11. As the sample size gets larger, what happens to the size of the correlation that is needed for significance? It gets smaller 12. For a two-tailed hypothesis test evaluating a Pearson correlation, what is stated by the null hypothesis? The population correlation is zero. 13. For the regression equation, Ŷ = –2 X + 6, if the X value is above the mean (positive deviation), what can be determined about the predicted Y value? The predicted Y value will be below the mean for the Y scores. 14. For linear regression, the value of  SS residual  can be computed directly by Σ( Y  – Ŷ ) 2 . True 15. A set of n = 25 pairs of scores (X and Y values) has a Pearson correlation of r = 0.80. How much of the variance for the Y scores is predicted by its relationship with X? 0.64 or 64% 16. For the linear equation Y = 2 X – 3, which of the following points will not be on the line? 3,0 17. For the linear equation Y = 2X + 4, if X increases by 1 point, how much will Y increase? 2 points

18. A set of n = 5 pairs of X and Y scores has Σ X = 15, Σ Y = 5, and Σ XY = 10. For these data, what is the value of SP (the TOP part of the ALTERNATIVE correlation formula on your formula sheet)? -5 19. A researcher obtains SS X = 20, SS Y = 5, and SP = 7 for a set of n = 25 pairs of scores. The Pearson correlation for these scores is r = 7/10 = 0.70. Hint: Look VERY carefully at your formula sheet, especially at the alternative definitional formula for r (wow, I can't believe I actually told you that). True 20.   What is the value of   SP   for the following set of data? Hint: SP=sum of cross products and is the TOP part of the ALTERNATIVE correlation formula on your formula sheet.  X     Y 4   3 1   2 1   5 2   6 The answer is -1 Lecture 22 (Chi-square) 1. The data for a chi-square test are called observed frequencies. True 2. How does the difference between fe and fo influence the outcome of a chi-square test? The larger the difference, the larger the value of chi-square and the greater the likelihood of rejecting the null hypothesis. 3. The observed frequencies for a chi-square test can be fractions or decimal values. False 4. What is referred to by the term observed frequencies ? The frequencies found in the sample data 5. Which of the following accurately describes the observed frequencies for a chi- square test? They are always whole numbers. 6. A chi-square test for goodness of fit has df = 2. How many categories were used to classify the individuals in the sample? 3 7. A researcher would like to test the claim that 9 out of 10 doctors prefer Brand X. A sample of 60 doctors is obtained and each is asked to compare Brand X with another leading brand. The data show that 48 of the doctors picked Brand X. If these data are evaluated using a chi-square test for goodness of fit, what is the expected frequency for Brand X? 54 8. Chi-square values are always greater than or equal to zero. True 9. What happens to the critical value for a chi-square test if the number of categories is increased? The critical value increases 10. For a fixed level of significance, the critical value for chi-square decreases as the size of the sample increases. False 11. A chi-square test for goodness of fit is used to examine the distribution of individuals across four categories, and a chi-square test for independence is used to examine

relative to some norms. The test scores range from 0 to 40. Which statistic should be used? Independent groups t-test 3. A cancer research organization has data on a large sample of the American population who have died over the past 20 years. They have information indicating the type of smoking done- by each individual (pipe smoker, cigar smoker, cigarette smoker, or nonsmoker). They also have the age at death for each person in their sample. The organization wants to see if their data supports the contention that smoking is related to age at death. Which statistic would they use? One Factor ANOVA 4. An experimenter is interested in hyperactivity and diet. She believes that the greater the amounts of certain food dyes that are consumed, the more hyperactive a child will be. She looks at children considered hyperactive, and children not considered hyperactive, and then measures the amount of these food dyes that each child consumes in an average month. The amounts vary from 0 to 500 mg. What statistic would enable her to determine if there is a relationship between hyperactivity and consumption of these food dyes? Independent groups t-test 5. An experimenter is interested in hyperactivity and diet. She believes that the greater the amounts of certain food dyes that are consumed, the more hyperactive a child will be. She measures the amount of food dye consumed on a scale from 0 to 500 mg and the degree of hyperactivity on a scale from 1 to 30. She wishes to use the scale to obtain some estimate of the degree of relationship between amount of these food dyes that are consumed, and the extent of hyperactivity. Which statistic should she use? R-squared or r 6. There is a good test for measuring authoritarian personality. An experimenter decides to see if being an authoritarian person is related to success in a particular profession. To this end, the experimenter selects 100 members of the profession, and on the basis of the test categorizes each of them as authoritarian or non-authoritarian. She then evaluates their individual professional histories, from which she categorizes each of them as being successful or unsuccessful in his or her profession. What statistical test would be useful in answering the question of whether authoritarian personality is related to success in this profession? Chi-square 7. A teacher sees students straggling into her class at highly diverse times. She secretly records when each person comes into her class. Everyone in the class at the bell gets a score of zero. Then, as each

late person comes in, the number of seconds after the bell that the person arrives is recorded. Number of seconds late, then, is each person's individual score. The scores ranged from 0 to 600 (for people who were 10 minutes late). The teacher also has each person's exam average over the semester. She wants some estimate of the degree of relationship between a person's lateness and his or her exam scores in her class. Which statistic should she use? r-squared or r 8. An experimenter wishes to know if strong doses of glucose can improve performance on an intelligence test. He gives an IQ test to a random sample of school children, twice to each child. One time, with each child, the test is taken after a large dose of glucose. The other time, with the same child, the test is taken without a prior dose of glucose. (The experimenter uses two equivalent forms of the same 1Q test.) Which statistic should he use? Dependent groups t test 9. You want to know whether working women consume different amounts of liquor than full-time housewives (measured in ounces per week). You wish to examine the data for possible differences, comparing women in urban, suburban, and rural areas. Which statistic should you use? Two Factor ANOVA 10. There is a notion that early discrimination training increases the IQ of children; that is, color discriminations (particularly subtle ones), discriminations among musical tones, etc., if fostered in children, are expected to increase IQ. A group of identical twins is used in an experiment to test this theory. One member of each twin pair gets this early discrimination training, but the other does not. Then, at a later date, their respective IQ scores are obtained. Which statistic would be used to test the hypothesis? Dependent groups t test