Stats 200 Review

STAT 200: Introduction to Statistics Page 1 of9

1. True or False. Show work.

(a) If A and B are disjoint, peA) = 0.4 and PCB) = 0.5, then peA OR B) = 0.9. (b) If the variance for a data set is zero, then all the observations in this data set must be

identicaL (c) There may be more than one mode in a data set. (d) A 90% confidence interval is wider than a 95% confidence interval of the same parameter. (e) In a right-tailed test, the value of the 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 of significance.

2. Choose the best answer. Show work.

(a) UMUC STAT Club wanted to estimate the study hours of STAT 200 students. One STAT 200 section was randomly selected and all students from that section were asked to fill out the questionnaire. This type of sampling is called:

(i) cluster (ii) convenience (iii) systematic (iv) stratified

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(b) A study was conducted at a local college to analyze the trend of average GPA of all students graduated from the college. According to the Registrar, the average GPA for students with economics major from the class of2016 is 3.5. The value 3.5 is a

(i) statistic (ii) parameter (iii) cannot be determined

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(c) The hotel ratings are usually on a scale from 0 star to 5 stars. The level of this measurement is

(i) interval (ii) nominal (iii) ordinal (iv) ratio

(d) 500 students took a chemistry test. You sampled 100 students to estimate the average score and the standard deviation. How many degrees of freedom were there in the estimation of the standard deviation? (i) 99 (ii) 100 (iii) 499 (iv) 500

(e) You choose an alpha level of 0.01 and then analyze your data. What is the probability that you will make a Type Ierror given that the null hypothesis is true? (i) 0.025 (ii) 0.05 (iii) 0.01 (iv) 0.10

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3. A random sample of 500 students was chosen from UMUC STAT 200 classes. The frequency distribution below shows the distribution for study time each week (in hours). Show work.

Study Time (in hours) Frequency Relative Frequency

0.0-5.0 40 5.1-10.0 100 10.1-15.0 0.25

15.1- 20.0 120

20.1- 25.0

Total 500

(a) Complete the frequency table with frequency and relative frequency. Express the relative frequency to two decimal places.

(b) What percentage of the study times was not more than 15 hours? (c) In what class interval must the median lie? 5.1-10.0, 10.1 -15.0, 15.1- 20.0, or 20.1 - 25.0?

Why?

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4. The five-number summary below shows the grade distribution of a STAT 200 quiz for a sample of 500 students.

20 45 65 75 tOO

o /0 20 30 40 50 60 70 80 90 100

Answer each question based on the given information, and explain your answer in each

case.

(a) What is the minimum in the grade distribution? (b) Which quarter has the smallest spread of data? What is that spread? (c) Find the interquartile range in the grade distribution. (d) Are there more students in the score band of 45- 65 or 65 - 85? Why? (e) Can the average score be determined based on the given information? Why or why not?

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5. A basket contains 1 white balls, 5 yellow balls, and 4 red balls. Consider selecting one ball at a time from the basket. Show work.

(a) Assuming the ball selection is without replacement. What is the probability that the first ball is white and the second ball is red?

(b) Assuming the ball selection is with replacement. What is the probability that the first ball is red and the second ball is also red?

6. There are 1000 juniors in a college. Among the 1000 juniors, 400 students are taking STAT200, and 700 students are taking PSYC300. There are 200 students taking both courses. Let S be the event that a randomly selected student takes STAT200, and P be the event that a randomly selected student takes PSYC300. Show work.

(a) Provide a written description of the complement event of(S ORP). (b) What is the probability of complement event of (S OR P)?

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7. Consider rolling a fair 6-faced die twice. Let A be the event that the sum of the two rolls is equal to 7, and B be the event that the first one is an odd number.

(a) What is the probability that the sum of the two rolls is equal to 7 given that the first one is an odd number? Show all work..

(b) Are event A and event B independent? Explain.

8. Answer the following two questions. Show all work.

(a) UMUC Stat Club is sending a delegate of2 members to attend the 2018 Joint Statistical Meeting in Vancouver. There are 10 qualified candidates. How many different ways can the delegate be selected?

(b) A bike courier needs to make deliveries at 5 different locations. How many different routes can he take?

STAT 200: Introductionto Statistics Page 8 of 9 9. Imagine you are in a game show. There are 20 prizes hidden on a game board with 100 spaces.

One prize is worth $50, nine are worth $20, and another ten are worth $10. You have to pay $5 to the host if your choice is not correct. Let the random variable x be the money you get or lose. Show all work.

(a) Complete the following probability distribution.

x P(x) -$5 $10 $20 $50

(b) What is your expected winning or loss in this game? Be specific in your answer whether it's winning or loss.

OM" S ~_il\

10. Mimi joined UMUC basketball team in spring 2017. On average, she is able to score 20% of the field goals. Assume she tries 10 field goals in a game.

(a) Let X be the number offield 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 3 of the 10 field goals. (round the answer to 3 decimal places) Show all work.

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11. A research concludes that the number of hours of exercise per week for adults is normally distributed with a mean of 4 hours and a standard deviation of 2.5 hours. Show all work.

(a) What is the probability that a randomly selected adult has at least 5 hours of exercise per week (round the answer to 4 decimal places)

(b) Find the 75t1t percentile for the distribution of exercise time per week. (round the answer to 2 decimal places)

12. 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.

(a) Consider all random samples of 64 test scores. What is the standard deviation of the sample means? (Round your answer to three decimal places)

(b) What is the probability that 64 randomly selected test scores will have a mean test score that is between 490 and 520? (Round your answer to four decimal places)

STAT 200: Introduction to Statistics Page 10 of 13. In a study designed to test the effectiveness of garlic for lowering cholesterol, 49 adults were

treated with garlic tablets. Cholesterol levels were measured before and after the treatment. The changes in their LDL cholesterol (in mg/dl.) have a mean of3 and standard deviation of 10. Construct a 95% confidence interval estimate of the mean change in LDL cholesterol after the garlic tablet treatment. Show all work.

14. Mimi conducted a survey on a random sample of 100 adults. 75 adults in the sample chose banana as his / her favorite fruit. Construct a 90% confidence interval estimate of the proportion of adults whose favorite fruit is banana. Show all work.

STAT 200· Introduction to Statjstjcs Page 11 of 15. A researcher is interested in testing the claim that more than 80% of the adults believe in

global warming. She conducted a survey on a random sample of 800 adults. The survey showed that 650 adults in the sample believe in global warming.

Assume the researcher wants to use a 0.05 significance level to test the claim.

(a) Identify the null hypothesis and the alternative hypothesis. (b) Determine the test statistic.Show all work (c) Determine the P-value for this test. Show all work (d) Is there sufficient evidence to support the claim that more than 80% of adults believe in global

warming? Explain.

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16. In a study of memory recall,S people were given 10 minutes to memorize a list of20 words. Each was asked to list as many of the words as he or she could remember both 1 hour and 24 hours later. The result is shown in the following table.

Number of Words Recalled Subject 1 hour later 24 hours later

1 13 13 2 18 14 3 12 11 4 15 14 5 11 11

Is there evidence to suggest that the mean number of words recalled after 1 hour exceeds the mean recall after 24 hours? Assume we want to use a 0.05 significance level to test the claim.

(a) Identify the null hypothesis and the alternative hypothesis. (b) Determine the test statistic. Show all work. (c) Determine the P-value. Show all work (d) Is there sufficient evidence to support the claim that the mean number of words recalled after

1 hour exceeds the mean recall after 24 hours? Justify your conclusion.

SIA.I.2D.Q,;Jotmductjoo tQ Statistics page 13 of 17. John oversees a bottle-filling machine in a company. The amount of fluid dispensed into each

bottle is approximately normally distributed with an unknown population standard deviation. On a particular day, a random sample of 400 bottles yielded a mean of357.2 mI and a standard deviation of 16.2 ml. John then concluded that the population standard deviation of the fluid dispense amount by the machine is greater than 15 mI.

The lead engineer wants to use a 0.05 significance level to test John's claim.

(a) Identify the null hypothesis and alternative hypothesis. (b) Determine the test statistic. Show all work. (c) Determine the P-value for this test. Show all work (d) Is there sufficient evidence to support John's claim that the population standard

deviation of the fluid dispense amount by the machine is greater than 15 m1? Explain.

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18. The UMUC Daily News reported that the color distribution for plain M&M's was: 35% brown, 30% yellow, 15% orange, 10% green, and 10% tan. Each piece of candy in a random sample of200 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

45 Green TanColor Brown Yellow

Number 80 30 15

(a) Identify the null hypothesis and the alternative hypothesis. (b) Determinethetest statistic.Show all work (c) Determine the P-value. Show all work (d) Is there sufficient evidence to support the claim that the published color distribution is

correct? Justify your answer.

STAT 20~. L' £ 'aC L!ii: L::__ P 01 If f 19. 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 exam score.

(a) Find an equation of the least squares regression line. Show all work (b) Based on the equation from part (a), what is the predicted final exam score if the average quiz

score is 80? Show all work f!W

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20. A study of 10 different weight loss programs involved 200 subjects. Each of the 10 programs had 20 subjects in it. The subjects were followed for 12 months. Weight change for each subject was recorded. We want to test the claim that the mean weight loss is the same for the 10 programs.

(a) Complete the following ANaVA table with sum of squares, degrees of freedom, and mean square (Show all work):

Sum of Squares Degrees of Freedom Mean Square Source of Variation

(SS) (dj) (MS)

Factor 53.6

(Between) Error

(Within)

Total 553.05 199 N/A

(b) Determine the test statistic. Show all work

(c) Determine the P-value. Show all work (d) Is there sufficient evidence to support the claim that the mean weight loss is the same for the

10 programs at the significance level of 0.05? Explain.