1. The number of hours that biology students study per week is normally distributed with a mean of 15 hours and a standard deviation of 5 hours.

a. Draw an approximate picture of the distribution of weekly hours studied for biology students.

b. If a student is chosen at random, what is the probability that the student studies less than 11 hours per week? Include a picture that graphically shows the portion of students that study less than 11 hours per week.

c. If a student is chosen at random, what is the probability that the student studies more than 20 hours per week? Include a picture that graphically shows the portion of students that study more than 20 hours per week.

d. What is the proportion of students that study between 8 and 20 hours per week? Include a picture that graphically shows this.

A study of undergraduate computer science students examined changes in major after the first year. The study examined the fates of 256 students who enrolled as first-year students in the same fall semester. The students were classified according to gender and their declared major at the beginning of the second year. For convenience we use the labels CS for computer science majors, EO for engineering and other science majors, and O for other majors. The explanatory variables included several high school grade summaries coded as 10 = A, 9 = A-, etc. Here are the mean high school mathematics grades for these students.

Describe the main effects and interaction using appropriate graphs and calculations.

1. A random sample of 120 ULS students yields a mean GPA of 2.71 with a sample standard deviation of 0.51. Construct a 95% confidence interval for the true mean GPA of all students at ULS. Find the minimum sample size required to estimate the true mean GPA at ULS to within 0.03 using a 95% confidence interval

2. Suppose we have 3 ULS student candidates running for the position of student representative, A, B, and C. We randomly select 160 ULS students. Of them, 120 vote for candidate A. Find a 95% confidence interval for the true proportion of the population of ULS students who will vote for candidate A. How many students must be surveyed in order to be 95% confident that the sampling percentage is in error by no more than 3 percentage points (or 0.03)?

According to the website www.collegedrinkingprevention.gov, “About 25 percent of college students report academic consequences of their drinking including missing class, falling behind, doing poorly on exams or papers, and receiving lower grades overall.” A statistics student is curious about drinking habits of students at his college. He wants to estimate the mean number of alcoholic drinks consumed each week by students at his college. He plans to use a 99% confidence interval. He surveys a random sample of 55 students. The sample mean is 3.69 alcoholic drinks per week. The sample standard deviation is 3.56 drinks.

Construct the 99% confidence interval to estimate the average number of alcoholic drinks consumed each week by students at this college.

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Your answer should be rounded to 2 decimal places.

The following frequency table summarizes the number of hours worked by a sample of 120 students in the same week. Hours worked by students Class (hours) Frequency (0, 10] 10 (10, 20] 60 (20, 30] 40 30 or more 10 Total 120 Show/hide advanced buttonsParagraph stylesBoldItalicUnordered listOrdered listLinkUnlinkInsert or edit imageInsert or edit an audio/video fileRecord audioRecord videoManage files

A) How many students worked more than 10 hours but less than or equal to 30 hours?

B) What is the relative frequency of students who worked more than 10 hours but less than or equal to 20 hours?

C) What is the cumulative frequency of students who worked less than or equal to 30 hours?

D) What are the units of measure for this sample of data?

•Exercise 1: It is assumed that 80% of the students pass the MBA 510 course. Calculate the following for a class of 15 students:

(a) the mean number of students expected to pass;

(b) the standard deviation;

(c) P(exactly 12 of the 15 students pass);

(d) P(at least 12 of the 15 students pass).

•Exercise 2: Five customers enter a store and make independent purchase decisions. The store’s records indicate that 20% of all customers who enter the store will make a purchase.         

(a) Does a general discrete probability distribution or the binomial distribution apply?

(b) Write the probability form applicable.  

Calculate the probability that:

(c) exactly 4 customers will make a purchase;

(d) less than 3 customers will make a purchase.

Please show all the work in Excel or Word.

A random sample of 15 students reporting anxiety at the student health

center were given written instructions for breathing exercises that they might

employ when a situation provoked anxious feelings. Another 13 received a

series of talk/ counselling sessions. After 6 weeks, all of the students were

administered the State-Trait Anxiety Inventory (STAI) which measures current

anxiety and a propensity for anxiety. The average score for the students with

the breathing instruction was 36 with a standard deviation of 8. The average for

the students receiving counseling was 32 with a standard deviation of 6 (higher

scores=higher anxiety). Is counselling better than the breathing exercises in

controlling anxiety among college students? Use alpha=.05 and assume that

STAI scores are normally distributed and have equal variances in the

populations.

I need a decision tree

Consider a scenario in which a college must recruit students. They have three options. They can do nothing. Alternatively, they could make their own ad campaign, spending $200,000. Their campaign has an 70% chance of being successful, which would mean bringing in 100 new students at $40,000 per student in tuition. Or the college could decide to spend $800,000 to hire a social media company to do the ads. This social media campaign has a 60% chance of being successful. If it is successful, there is an 75% chance in will bring in 100 new students. If it is not successful, there is a 10% chance it will bring in 100 new students. Otherwise it will bring in no new students. What should the college do to maximize expected value? Show your work including expected values.

1. A professor hypothesizes that students who earn a C or better in her class spend more time outside of class studying than students who receive a D or F. She collects the following data from two samples of students. What does she conclude?

Number of hours studying per week for C or better students:
8, 4, 4, 2, 1, 5, 3, 2, 3

Number of hours studying per week for D or F students:
6, 2, 1, 0, 3, 2, 1

1. Null hypothesis:
2. Alternative hypothesis:
3. Statistical test (be specific!):
4. Significance level: alpha = .05
5. degrees of freedom:
6. Critical region (t-value):
7. Calculated t (show your work):
8. Decision:

In a recent survey of 150 students at a large community college, 86 students said they were “regular” coffee drinkers. It is known that 64% of all students at that community college are “regular” coffee drinkers. Use this information to compute necessary quantities, and fill in the blanks: The average distance between the values of the sample proportion (from all possible random samples of 150 students from this community college) of "regular" coffee drinkers and the population proportion 0.64 of "regular" coffee drinkers in this community college is approximately_________. We estimate that the values of the sample proportion (from all possible random samples of 150 students from this community college) of "regular" coffee drinkers vary from the population proportion of "regular" coffee drinkers in this community college of 0.64 by about _________ , on average.