Grade school students, especially the ones in higher grades, tend to spend a lot of time on the computer already. The average amount of time 4th grade boys spend on the computer is 5 hours per week, with a standard deviation of 1 hour. For 5th grade boys the average increases to 7 hours per week with a standard deviation of 1.5 hours. Random sample of 20 4th grade students and 25 5th grade students are to be selected. What is the expected value for the difference in sample means (5th 4th grade)?
Q. 2An ESP experiment is done in which a participant guesses which of 4 cards the researcher has randomly picked, where each card is equally likely. This is repeated for 200 trials. The null hypothesis is that the subject is guessing, while the alternative is that the subject has ESP and can guess at higher than the chance rate. Which of the following would be a Type 1 error in this situation?
a. Declaring somebody has ESP when they actually don't have ESP.
b. Declaring somebody does not have ESP when they actually do.
c. Analyzing the data with a confidence interval rather than a significance test.
d. Making a mistake in the calculations of the significance test.
Q. 3Many adults complain they do not get enough sleep at night. What happens when these adults have children? Independent random samples of 150 adults who do not have children in the house and 130 adults who do have children in the house are selected. The average amount of sleep the adults without children had was 7.1 hours with a standard deviation of 0.7 hours. The average amount of sleep the adults with children had was 6.5 hours with a standard deviation of 0.8 hours. What is the estimate for the standard deviation of the sampling distribution of the difference in sample means?
Q. 4An ESP experiment is done in which a participant guesses which of 4 cards the researcher has randomly picked, where each card is equally likely. This is repeated for 200 trials. The null hypothesis is that the subject is guessing, while the alternative is that the subject has ESP and can guess at higher than the chance rate. The subject actually gets 70 correct answers. Which of the following describes the probability represented by the p-value for this test?
a. The probability that the subject has ESP
b. The probability that the subject is just guessing.
c. The probability of 70 or more correct guesses if the subject has ESP.
d. The probability of 70 or more correct guesses if the subject is guessing at the chance rate.
Q. 5Many adults complain they do not get enough sleep at night. What happens when these adults have children? Independent random samples of 150 adults who do not have children in the house and 130 adults who do have children in the house are selected. The average amount of sleep the adults without children had was 7.1 hours with a standard deviation of 0.7 hours. The average amount of sleep the adults with children had was 6.5 hours with a standard deviation of 0.8 hours. What is the estimate for the difference in mean hours slept at night between adults with and adults without children?
Q. 6An ESP experiment is done in which a participant guesses which of 4 cards the researcher has randomly picked, where each card is equally likely. This is repeated for 200 trials. The null hypothesis is that the subject is guessing, while the alternative is that the subject has ESP and can guess at higher than the chance rate. What is the correct statement of the null hypothesis that the person does not have ESP?
a. H0: p = 0.5
b. H0: p = 4/200
c. H0: p = 1/4
d. H0: p > 1/4
Q. 7College students spend a lot of their money, not on things they would like to buy, but on text books. College text books have increased in price significantly over the past few years. The amount students spend on text books is approximately normally distributed with a standard deviation of 50 . The average amount spent on books each semester is 340 for undergraduate students and 250 for graduate students. Independent random samples of 100 undergraduate students and 80 graduate students are to be selected and the average amount they spent on text books last semester is to be compared (undergraduate graduate). What is the probability that the undergraduate students in the sample spent more on books, on average, than the graduate students in the sample?
Q. 8Past data indicates an 80 (0.8) success rate in treating a certain medical problem. A new treatment is used on 100 patients in a clinical trial. It is successful in 87 (0.87) of the cases. What is the value of the z-score that can be used to test the null hypothesis that the success rate is 80?
a. 7
b. 2
c. 1.75
d. -1.75
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