STAT 200 Week 7 Homework
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.
Lane Chap. 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% freshmen, 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.
Decide whether the following statements are true or false.
70. The standard deviation of the chi-square distribution is twice the mean.
Usethefollowinginformationtoanswerthenextexercise:Supposeanairlineclaimsthatitsflightsareconsistently ontimewithanaveragedelayofatmost15minutes.Itclaimsthattheaveragedelayissoconsistentthatthevarianceisno 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= ________
66. Can a coefficient of determination be negative? Why or why not?
The cost of a leading liquid laundry detergent in different sizes is given.
Cost per ounces
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. Istheleast-squareslinevalidforpredictingwhata300-ouncesizeofthelaundrydetergentwouldyoucost?Why or why not?
j. What is the slope of the least-squares (best-fit) line? Interpret the slope.