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Chapter 10: Q. AP3.20 (page 703)

Final grades for a class are approximately Normally distributed with a mean of 76and a standard deviation of 8. A professor says that the top10%of the class will receive an A, the next20%a B, the next 40%a C, the next 20%a D, and the bottom 10%an F. What is the approximate maximum grade a student could attain and still receive an F for the course?

a.70b.69.27c.65.75d.62.84e.57

Short Answer

Expert verified

The correct option is:

c.65.75is the approximate maximum grade a student could attain and still receive an F for the course.

Step by step solution

01

 Step 1: Given information 

We have to tell about the approximate maximum grade a student could attain and still receive an F for the course.

02

Explanation 

While much information is provided, the inquiry solely concerns the value at which a student will receive an F. (but anything more will be a D). The problem further specifies that anything less than 10%will result in an F.

For a mean of 76and a standard deviation of 1, we don't have a normal distribution table. The trick is to convert to X using the Z score form after using the standardised normal table.

Then usez0=x0-μσ

Multiply by 8and add 76to get the answer.

x0=-1.28*8+76≈65.75

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Most popular questions from this chapter

Mrs. Woods and Mrs. Bryan are avid vegetable gardeners. They use different fertilizers, and each claims that hers is the best fertilizer to use when growing tomatoes. Both agree to do a study using the weight of their tomatoes as the response variable. Each planted the same varieties of tomatoes on the same day and fertilized the plants on the same schedule throughout the growing season. At harvest time, each randomly selects 15 tomatoes from her garden and weighs them. After performing a two-sample t test on the difference in mean weights of tomatoes, they gett=5.24 andP=0.0008. Can the gardener with the larger mean claim that her fertilizer caused her tomatoes to be heavier?

a. Yes, because a different fertilizer was used on each garden.

b. Yes, because random samples were taken from each garden.

c. Yes, because the P-value is so small.

d. No, because the condition of the soil in the two gardens is a potential confounding variable.

e. No, because15<30

Music and memory Refer to Exercise 87.

a. Construct and interpret a 99%confidence interval for the true mean difference. If you already defined the parameter and checked conditions in Exercise87, you don’t need to do them again here.

b. Explain how the confidence interval provides more information than the test in Exercise .

Which of the following will increase the power of a significance test?

a. Increase the Type II error probability.

b. Decrease the sample size.

c. Reject the null hypothesis only if the P-value is less than the significance level.

d. Increase the significance level α.

e. Select a value for the alternative hypothesis closer to the value of the null hypothesis.

A scatterplot and a least-squares regression line are shown in the figure. What effect does point P have on the slope of the regression line and the correlation?

a. Point P increases the slope and increases the correlation.

b. Point P increases the slope and decreases the correlation.

c. Point P decreases the slope and decreases the correlation.

d. Point P decreases the slope and increases the correlation .

e. No conclusion can be drawn because the other coordinates are unknown.

Men versus women The National Assessment of Educational Progress (NAEP)

Young Adult Literacy Assessment Survey interviewed separate random samples of840

men and 1077women aged 21to 25years.

The mean and standard deviation of scores on the NAEP’s test of quantitative skills were x1=272.40and s1=59.2for the men in the sample. For the women, the results were x ̄2=274.73and s2=57.5.

a. Construct and interpret a 90% confidence interval for the difference in mean score for

male and female young adults.

b. Based only on the interval from part (a), is there convincing evidence of a difference

in mean score for male and female young adults?
See all solutions

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