Lane Chapter 14
2. The formula for a regression equation is Y’ = 2X + 9.
a. What would be the predicted score for a person scoring 6 on X?
b. If someone’s predicted score was 14, what was this person’s score on X?
6. For the X, Y data below, compute:
a. r and determine if it is significantly different from zero.
b. the slope of the regression line and test if it differs significantly from zero.
c. the 95% confidence interval for the slope.
X
Y
4
6
3
7
5
12
11
17
10
9
14
21
Lane Chapter 17
5. At a school pep rally, a group of sophomore students organized a free raffle for prizes. They claim that they put the names of all of the students in the school in the basket and that they randomly drew 36 names out of this basket. Of the prize winners, 6 were freshmen, 14 were sophomores, 9 were juniors, and 7 were seniors. The results do not seem that random to you. You think it is a little fishy that sophomores organized the raffle and also won the most prizes. Your school is composed of 30% freshman, 25% sophomores, 25% juniors, and 20% seniors.
a. What are the expected frequencies of winners from each class?
b. Conduct a significance test to determine whether the winners of the prizes were distributed throughout the classes as would be expected based on the percentage of students in each group. Report your Chi Square and p values.
c. What do you conclude?
14. A geologist collects hand-specimen sized pieces of limestone from a particular area. A qualitative assessment of both texture and color is made with the following results. Is there evidence of association between color and texture for these limestones? Explain your answer.
Colour
Texture
Light
Medium
Dark
Fine
Medium
Coarse
4
5
21
20
23
23
8
12
4
Illowsky Chapter 11
Decide whether the following statements are true or false.
70. The standard deviation of the chi-square distribution is twice the mean.
Use the following information to answer the next twelve exercises: Suppose an airline claims that its flights are consistently on time with an average delay of at most 15 minutes. It claims that the average delay is so consistent that the variance is no more than 150 minutes. Doubting the consistency part of the claim, a disgruntled traveler calculates the delays for his next 25 flights. The average delay for those 25 flights is 22 minutes with a standard deviation of 15 minutes.
113. df = ________
Illowsky Chapter 12
12.3 The Regression Equation
66. Can a coefficient of determination be negative? Why or why not?
Use the following information to answer the next two exercises. The cost of a leading liquid laundry detergent in different sizes is given in Table 12.31
Size (ounces)
Cost ($)
Cost per ounce
16
3.99
32
4.99
64
5.99
200
10.99
82.
a. Using “size” as the independent variable and “cost” as the dependent variable, draw a scatter plot.
b. Does it appear from inspection that there is a relationship between the variables? Why or why not?
c. Calculate the least-squares line. Put the equation in the form of: ŷ = a + bx
d. Find the correlation coefficient. Is it significant?
e. If the laundry detergent were sold in a 40-ounce size, find the estimated cost.
f. If the laundry detergent were sold in a 90-ounce size, find the estimated cost.
g. Does it appear that a line is the best way to fit the data? Why or why not?
h. Are there any outliers in the given data?
i. Is the least-squares line valid for predicting what a 300-ounce size of the laundry detergent would you cost? Why or why not?
j. What is the slope of the least-squares (best-fit) line? Interpret the slope.
Quiz 3
This quiz has more conceptual questions, because I think they’re important. Be sure to understand the 2×2 box dealing with Type I and Type II errors, alpha, beta, and power.
Each multiple choice questions is worth 0.50 point. Other questions are worth two points.
1. (0.50 point) I hypothesized that girls in my class have the same blood pressure levels as boys. The probability value for my null hypothesis was 0.15. So I conclude that the blood pressures of the girls were higher than boys’. Which kind of mistake did I make?
a. Type I error
b. Type II error
c. Type I and Type II error
d. I did not make any mistake
2. (0.50 point) If a statistical test result is not significant at the 0.05 level, then we can conclude:
a. It is not significant at 0.10 level
b. It must be significant at 0.01 level
c. It must be significant above 0.05 level
d. It is not significant at 0.01 level
3. (2 points) A researcher posed a null hypothesis that there was no significant difference between boys and girls on a standard memory test. She randomly sampled 100 girls and 100 boys in a community and gave them the standard memory test. The mean score for girls was 70 and the standard deviation of mean was 5.0. The mean score for boys was 65 and the standard deviation of mean was 5.0. What is the standard error of the difference in means?
4. (0.50 point) If power is big, you can assume:
a. The significance level set by the researcher must be high
b. We increase the probability of type I error
c. Your study result will be more likely to be inconclusive
d. The difference between the means is more likely to be detected
5. (0.50 point) If the probability that you will correctly reject a false null hypothesis is 0.80 at 0.05 significance level. Therefore, α is__ and β is__.
a. 0.05, 0.80
b. 0.05, 0.20
c. 0.95, 0.20
d. 0.95, 0.80
6. (2 points) The population has a mean of 678 and the population standard deviation is known to be 58.3. Use a 0.05 level of significance to test the claim that the sample scores listed below came from the population. Identify hypotheses, test statistic, P-value or critical value, conclusion about the null, and final conclusion that addresses the original claim.
714 751 664 789 818 779 698 836 753 834 693 802
7. (2 points) I am looking to move to either Mississippi or Arkansas, depending on the cost of housing. Below are the costs (in thousands, hypothetically) of 12 houses in each location based upon a simple random selection:
Mississippi: 155 142 149 130 151 163 151 142 156 133 138 161
Arkansas: 133 140 142 131 134 129 128 140 140 140 137 143
Use a 0.05 significance level to test the claim that the mean cost of houses in Mississippi is greater than the mean cost in Arkansas. Be sure to give the hypotheses, the test statistic with a p-value, and a conclusion.
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