1. True or False. Justify for fullcredit.
(a) A is an event, and Ac is the complement of A, then P(A AND Ac ) =0.
(b) If the variance of a data set is 0, then all the observations in this data set must bezero.
(c) If a 95% confidence interval for a population mean contains 1, then the 90% confidence interval for the same parameter must contain1
(d) When plotted on the same graph, a distribution with a mean of 40 and a standard deviation of 10 will look more spread out than a distribution with a mean of 50 and standard deviation of5.
(e) In a two-tailed test, the value of a test statistic is 2. The test statistic follows a distribution with the distribution curve shown below. If we know the shaded area is 0.03, then we have sufficient evidence to reject the null hypothesis at 0.05 level ofsignificance.
2. Choose the best answer. Justify for fullcredit.
(a) A study was conducted at a local college to analyze the average GPA of students graduated from UMUC in 2015. 100 students graduated from UMUC in 2015 were randomly selected, and the average GPA for the group is 3.5. The value 3.5 isa
(i) statistic
(ii) parameter
(iii) cannot bedetermined
(b) The hotel ratings are usually on a scale from 0 star to 5 stars. The level of this measurementis
(i) interval
(ii) nominal
(iii) ordinal
(iv) ratio
(c) On the Election Day, UMUC News Club organized an exit poll in which specific polling stations were randomly selected and all voters were surveyed as they left those polling stations. This type of sampling iscalled:
(i) cluster
(ii) convenience
(iii) systematic
(iv) stratified
3. Choose the best answer. Justify for fullcredit.
(a) A study of 10 different weight loss programs involved 500 subjects. Each of the 10 programs had 50 subjects in it. The subjects were followed for 12 months. Weight change for each subject was recorded. You want to test the claim that the mean weight loss is the same for the 10 programs. What statistical approach should beused?
(i) t-test
(ii) linearregression
(iii) ANOVA
(iv) confidenceinterval
(b) A STAT 200 instructor teaches two classes. She wants to test if the variances of the score distribution for the two classes are different. What type of hypothesis test should sheuse?
(i) t-test for two independentsamples
(ii) t-test for matchedsamples
(iii) z-test for twosamples
(iv) F-test
4. A random sample of 100 students was chosen from UMUC STAT 200 classes. The frequency distribution below shows the distribution for study time each week (in hours). (Show all work. Just the answer, without supporting work, will receive nocredit.)
|
Study Time (in hours)
|
Frequency
|
Relative Frequency
|
|
0.0 - 4.9
|
5
|
|
|
5.0 - 9.9
|
13
|
|
|
10.0 - 14.9
|
|
0.22
|
|
15.0 -19.9
|
42
|
|
|
20.0 - 24.9
|
|
|
|
Total
|
100
|
|
(a) Complete the frequency table with frequency and relative frequency. Express the relative frequency to three decimalplaces.
(b) What percentage of the study times was at least 15hours?
(c) Does this distribution have positive skew or negative skew? Why or whynot?
5. The five-number summary below shows the grade distribution of a STAT 200 quiz for a sample of 1000students.
Answer each question based on the given information, and explain your answer in each case.
(a) What is the interquartile range in the gradedistribution?
(b) Which score band has the fewest students?
(i) 20 -60
(ii) 60 - 75
(iii) 75 -90
(iv) Cannot bedetermined
(c) How many students are in the score band between 75 and100?
6. Consider selecting one card at a time from a 52-card deck. What is the probability that the first card is from the suit of hearts and the second card is also from the suit of hearts? (Note: There are 13 cards from the suit of hearts in a deck of cards) (Show all work. Just the answer, without supporting work, will receive nocredit.)
(a) Assuming the card selection is withoutreplacement.
(b) Assuming the card selection is withreplacement.
7. There are 1000 students in a high school. Among the 1000 students, 150 students take AP Statistics, and 300 students take AP French. 100 students take both AP courses. Let S be the event that a randomly selected student takes AP Statistics, and F be the event that a randomly selected student takes AP French. Show all work. Just the answer, without supporting work, will receive nocredit.
(a) Provide a written description of the complement event of (S ORF).
(b) What is the probability of complement event of (S ORF)?
8. Consider rolling a fair 6-faced die twice. Let A be the event that the sum of the two rolls is at most 6, and B be the event that the first one is an evennumber.
(a) What is the probability that the sum of the two rolls is at most 6 given that the first one is an even number? Show all work. Just the answer, without supporting work, will receive nocredit.
(b) Are event A and event B independent?Explain.
9. There are 6 books in the "Statistics is Fun" series. (Show all work. Just the answer, without supporting work, will receive nocredit).
(a) How many different ways can Mimi arrange the 6 books in her bookshelf?
(b) Mimi plans on bringing three of the six books with her in a road trip. How many different ways can the two books beselected?
10. Assume random variable x follows a probability distribution shown in the table below. Determine the mean and standard deviation of x. Show all work. Just the answer, without supporting work, will receive nocredit.
|
x
|
-2
|
-1
|
0
|
1
|
2
|
|
P(x)
|
0.1
|
0.4
|
0.1
|
0.1
|
0.3
|
11. Mimi joined UMUC basketball team since summer 2016. On average, she is able to score 30% of the field goals. Assume she tries 15 field goals in agame.
(a) Let X be the number of field goals that Mimi scores in the game. As we know, the distribution of X is a binomial probability distribution. What is the number of trials (n), probability of successes (p) and probability of failures (q),respectively?
(b) Find the probability that Mimi scores at least 2 of the 15 field goals. (round the answer to 3 decimal places) Show all work. Just the answer, without supporting work, will receive nocredit.
12. A research concludes that the number of hours of exercise per week for adults is normally distributed with a mean of 3.5 hours and a standard deviation of 3 hours. Show all work. Just the answer, without supporting work, will receive nocredit.
(a) Find the 75th percentile for the distribution of exercise time per week. (round the answer to 2 decimal places)
(b) What is the probability that a randomly selected adult has more than 5 hours of exercise per week? (round the answer to 4 decimalplaces)
13. Assume the SAT Mathematics Level 2 test scores are normally distributed with a mean of 500 and a standard deviation of 100. Show all work. Just the answer, without supporting work, will receive no credit.
(a) Consider all random samples of 100 test scores. What is the standard deviation of the sample means?
(b) What is the probability that 100 randomly selected test scores will have a mean test score that is between 490 and510?
14. An insurance company checks police records on 1200 randomly selected auto accidents and notes that teenagers were at the wheel in 180 of them. Construct a 90% confidence interval estimate of the proportion of auto accidents that involve teenage drivers. Show all work. Just the answer, without supporting work, will receive nocredit.
15. A city built a new parking garage in a business district. For a random sample of 100 days, daily fees collected averaged $1,800, with a standard deviation of $500. Construct a 90% confidence interval estimate of the mean daily income this parking garage generates. Show all work. Just the answer, without supporting work, will receive nocredit.
16. ABC Company claims that the proportion of its employees investing in individualinvestment accounts is higher than national proportion of 50%. A survey of 100 employees in ABC Company indicated that 58 of them have invested in an individual investmentaccount.
Assume Mimi wants to use a 0.10 significance level to test the claim.
(a) Identify the null hypothesis and the alternativehypothesis.
(b) Determine the test statistic. Show all work; writing the correct test statistic, without supporting work, will receive nocredit.
(c) Determine the P-value for this test. Show all work; writing the correct P-value, without supporting work, will receive nocredit.
(d) Is there sufficient evidence to support ABC Company's claim that the proportion of its employees investing in individual investment accounts is higher than 50%?Explain.
17. Mimi was curious if regular excise really helps weight loss, hence she decided to perform a hypothesis test. A random sample of 5 UMUC students was chosen. The students took a 30- minute exercise every day for 6 months. The weight was recorded for each individual before and after the exercise regimen. Does the data below suggest that regular exercise helps weight loss?
|
Weight (pounds)
|
|
Subject
|
Before
|
After
|
|
1
|
160
|
120
|
|
2
|
170
|
168
|
|
3
|
190
|
175
|
|
4
|
165
|
165
|
|
5
|
200
|
190
|
Assume we want to use a 0.05 significance level to test the claim.
(a) Identify the null hypothesis and the alternativehypothesis.
(b) Determine the test statistic. Show all work; writing the correct test statistic, without supporting work, will receive nocredit.
(c) Determine the p-value. Show all work; writing the correct critical value, without supporting work, will receive nocredit.
(d) Is there sufficient evident to support the claim that regular exercise helps weight loss? Justify yourconclusion.
18. In a pulse rate research, a simple random sample of 120 men results in a mean of 80 beats per minute, and a standard deviation of 11 beats per minute. Based on the sample results, the researcher concludes that the pulse rates of men have a standard deviation greater than 10 beats per minutes. Use a 0.10 significance level to test the researcher'sclaim.
(a) Identify the null hypothesis and alternativehypothesis.
(b) Determine the test statistic. Show all work; writing the correct test statistic, without supporting work, will receive nocredit.
(c) Determine the P-value for this test. Show all work; writing the correct P-value, without supporting work, will receive nocredit.
(d) Is there sufficient evidence to support the researcher's claim?Explain.
19. The UMUC Daily News reported that the color distribution for plain M&M's was: 40% brown, 20% yellow, 20% orange, 10% green, and 10% tan. Each piece of candy in a random sample of 100 plain M&M's was classified according to color, and the results are listed below. Use a 0.05 significance level to test the claim that the published color distribution is correct. Show all work and justify youranswer.
|
Color
|
Brown
|
Yellow
|
Orange
|
Green
|
Tan
|
|
Number
|
45
|
21
|
11
|
8
|
15
|
(a) Identify the null hypothesis and the alternativehypothesis.
(b) Determine the test statistic. Show all work; writing the correct test statistic, without supporting work, will receive nocredit.
(c) Determine the p-value. Show all work; writing the correct critical value, without supporting work, will receive nocredit.
(d) Is there sufficient evidence to support the claim that the published color distributionis correct? Justify youranswer.
20. A STAT 200 instructor believes that the average quiz score is a good predictor of final exam score. A random sample of 10 students produced the following data where x is the average quiz score and y is the final examscore.
|
Color
|
Brown
|
Yellow
|
Orange
|
Green
|
Tan
|
|
Number
|
45
|
21
|
11
|
8
|
15
|
(a) Find an equation of the least squares regression line. Show all work; writing the correct equation, without supporting work, will receive nocredit.
(b) Based on the equation from part (a), what is the predicted final exam score if the average quiz score is 95? Show all work and justify youranswer.