Midterm 2_PracticeQuestions_withAnswers-1

1. Suppose that your score on a test is 95. From which of the following distributions would you prefer your score to be? **~N ( μ , s ) denotes normally distributed with mean μ and standard deviation s . a) ~N(85, 10) b) ~N(95, 10) c) ~N(95, 15) d) ~N(80, 20) e) ~N(105, 15) (a) Hint 1: calculate z-scores for each of the 5 alternatives and pick the highest one. Hint 2: there are time saving strategies to eliminate some of the alternatives right off the bat without having to calculate z-scores for those. 2. The raw and z-scores of your mark in the Math exam were 70 and 1, respectively. Given that the standard deviation of the distribution of all scores in this exam were 20, what is the raw score and percentile rank of a student whose z-score was –1? (assume normal distribution). 30; 16% 3. Your finished the Vancouver Marathon in 4 hours and 30 minutes. This was longer (i.e. a slower run) than 65% of all the runners who participated. Assuming finish time is normally distributed with a mean finish time of 4 hours, what is the standard deviation? Runners were considered to have completed the marathon if they finished the course in 6 hours and 30 minutes or less; others were disqualified. What percentage of runners were disqualified from the race? a. Standard deviation: 76.92 minutes b. approx. 2.6% were disqualified 4. Two Vancouver meteorologists review the output of the same weather forecast model. Every morning, they predict if it will rain at 4pm on that day. Meteorologist A is more likely to announce it will rain based on this model output compared to Meteorologist B. Which one of the following is most likely to be true: a. Meteorologist A will have more misses and more correct rejects. b. Meteorologist A will have more hits and more false alarms. c. Meteorologist A will have more hits and more misses. d. Meteorologist A will have less hits and less false alarms. e. Meteorologist A will have more correct rejects and more false alarms. (b) 5. Each morning a Vancouver meteorologist forecasts the weather for the day stating whether it will rain during the evening rush hour based on her interpretation of an atmospheric model issued by Environment Canada. In the long run, which one of the following may help her decrease her false alarms and increase hits? Choose all that applies. (i) consulting multiple atmospheric models (ii) using a more liberal criterion (iii) using a more conservative criterion (iv) training on atmospheric model interpretation (v) forecasting rain more often (vi) forecasting clear skies more often (i) and (iv) 6. You think you inadvertently offended the server upon entering a restaurant. When he brought your drinks over, you noticed that your glass is a bit short of being full. When

you point this out to the server, he argues that the machine automatically dispenses the drink at the press of a button and fills it up to a slightly different level each time. You are skeptical of this explanation and decided that this is the server's way of getting "revenge". If the waiter was in fact telling the truth, your decision was a case of: a) False Alarm b) Miss c) Hit d) Correct reject (a) 7. The internal response curves for signal absent and signal present conditions shown above are both normally distributed with the same standard deviation, a . Criterion is set at 2a . For (i—vii) please refer to this figure and the information provided. (i) What is the false alarm rate? 2.5% (ii) What is the hit rate? 50% (iii) What is the miss rate? 50% (iv) What is the correct reject rate? 97.5% (v) What is d-prime? 2 (vi) What would be the criterion value that generates a false alarm rate of 16%? a (vii) What would d-prime be if criterion was set at a ? 2 8. A new medical test introduced to detect a genetic abnormality of a fetus based on blood drawn from the mother has a false alarm rate of 1%. What is the hit rate of the test? a. 16% b. 50% c. 84% d. 99% e. Can not be determined based on the information provided. (e) 9. You got a score of 50 in your Psychology exam and the professor informed you that scores in the exam were ~N(60, 5). The z-score and percentile rank of your exam score were: a. z = -1, percentile rank » 98% b. z = 1, percentile rank » 98% c. z = -2, percentile rank » 2.5%

The findings are as follows: Drug Group (n=50): Mean number of connections = 1200 Standard deviation = 100 Placebo Group (n=50): Mean number of connections = 1100 Standard deviation = 90 Calculate Cohen's d to determine the effect size of the drug on increasing the number of neuronal connections. Interpret whether this is a small, medium or large effect. Cohen's d » 1.05 This is a large effect