6. The college bookstore tells prospective students that the average cost of its textbooks is $42 with a standard deviation of $2.50. A group of smart statistics students thinks that the average cost is higher. In order to test the bookstore’s claim against their alternative, the students will select a random sample of size 100. Assume that the mean from their random sample is $42.80. Perform a hypothesis test at the 5% level of significance and state your decision

PHC 131

PHC 131

The number of pizzas consumed per month by university students is normally distributed with a mean of 6 and a standard deviation of 4.

A. What proportion of students consume more than 7 pizzas per month?

Probability =

B. What is the probability that in a random sample of size 8, a total of more than 40 pizzas are consumed? (Hint: What is the mean number of pizzas consumed by the sample of 8 students?)

Probability =

The author of an introductory textbook on business statistics completed a study using 30 undergraduate statistics students selected at random from a large university. The students were given a comprehensive test that took them an average of 90 minutes to complete with a sample standard deviation of 15 minutes. Construct and interpret the 90% confidence interval for the population mean time it would take for all statistics students at the university to complete this test.

college students often make up a substantial portion of the population of college cities and towns. State College, Pennsylvania, ranks first with 71.1 of its population made up of college students. What is the probability that in a random sample 134 of people from State College, more than 50 are not college students? Round the final answer to at least decimal places and intermediate -value calculations to decimal places.

A professor at a local community college noted that the grades of his students were normally distributed with a mean of 74 and a standard deviation of 10. The professor has informed us that 6.4 percent of his students received A's while only 2.5 percent of his students failed the course and received F's. What is the minimum score needed to earn an A? Enter your answer rounded to one decimal place.

The age of a students in a class is a normal random variable. There are 80 students in our class. I select 9 students randomly and calculate the mean of their ages (sample mean). I repeat this experiment 1,000,000 times. Then I calculate the mean and standard deviation of the 1,000,000 sample means that I measured; the calculated values are 22 and 4, respectively. What is the probability that the age of a randomly selected student in the class is below 20?

The college bookstore tells prospective students that the average cost of its textbooks is $52 with a standard deviation of $4.50. A group of smart statistics students thinks that the average cost is higher. In order to test the bookstore’s claim against their alternative, the students will select a random sample of size 100. Assume that the mean from their random sample is $52.80. Test at 10% significance level.

--> Perform a hypothesis test and state your decision.

If the sample proportion of first-year students who suffer from depression is 328/450

1- Find and interpret the 95% condence interval for the proportion of students who are suffering from depression. Is there evidence to suggest that more than half

of the population of first-year students suffer from depression? Explain.

2- Give an explanation for your conclusion in part 1.

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