AP Stats Ch2

Birthweights at a local hospital have a Normal distribution with a mean of 110 oz. and a standard deviation of 15 oz. Which of the following is the proportion of infants with birthweights under 95 oz.?

0.160

A company produces ceramic floor tiles that are supposed to have a surface area of 16.0 square inches. Due to variability in the manufacturing process, the actual surface area has a Normal distribution with a mean of 16.1 square inches and a standard deviation of 0.2 square inches. The proportion of tiles produced by the process with surface area less than 16.0 square inches is

0.3085.

Suppose that scores on a certain IQ test are Normally distributed with mean 110 and standard deviation 15. Then about 40% of the scores are between

102 and 118.

Let X denote the time taken for a computer link to be made between the terminal in an executive's office and the computer at a remote factory site. It is known that X has a Normal distribution with a mean of 15 seconds and a standard deviation of 3 seconds. On 90% of the occasions the computer link is made in less than

18.84 seconds.

Consider the following cumulative relative frequency graph of the scores of students in an introductory statistics course: A grade of C or C+ is assigned to a student who scores between 55 and 70. The percentage of students who obtained a grade of C or C+ is

20%

Use Figure 2-1. For this density curve, what percent of the observations lie above 4?

20%

A company produces packets of soap powder that are labeled "Giant Size 32 Ounces." The actual weight of soap powder in a box has a Normal distribution with a mean of 33 oz. and a standard deviation of 0.7 oz. 95% of packets actually contain more than x oz. of soap powder. What is x?

31.85

Entomologist Heinz Kaefer has a colony of bongo spiders in his lab. There are 1000 adult spiders in the colony, and their weights are Normally distributed with mean 11 grams and standard deviation 2 grams. About how many spiders are there in the colony which weigh more than 12 grams?

310

If the heights of 99.7% of American men are between 5' 0" and 7' 0", what is your estimate of the standard deviation of the height of American men?

4"

IQs among undergraduates at Mountain Tech are approximately Normally distributed. The mean undergraduate IQ is 110. About 95% of undergraduates have IQs between 100 and 120. The standard deviation of these IQs is about

5.

A soft-drink machine can be regulated so that it discharges an average of μ oz. per cup. If the ounces of fill are Normally distributed with a standard deviation of 0.4 oz., what value should μ be set at so that 98% of 6-oz. cups will not overflow?

5.18

The 35th percentile of a population is the number x such that

65% of the population scores are above x.

The five-number summary of the distribution of 316 scores on a statistics exam is0 26 31 36 50. The scores are approximately Normal. The standard deviation of test scores must be about

7.5.

The time to complete a standardized exam is approximately Normal with a mean of 70 minutes and a standard deviation of 10 minutes. How much time should be given to complete the exam so that 80% of the students will complete the exam in the time given?

78.4 minutes

Use Figure 2-1. For this density curve, which of the following is true?

All of the above.

A company produces packets of soap powder labeled "Giant Size 32 Ounces." The actual weight of soap powder in a box has a Normal distribution with a mean of 33 oz. and a standard deviation of 0.8 oz. What proportion of packets are underweight (i.e., weigh less than 32 oz.)?

0.106.

Which of the following dot plots would best be approximated by a Normal distribution?

E

A standard score describes

How far a particular score is from the mean.

Jack and Jill are both enthusiastic players of a certain computer game. Over the past year, Jack's mean score when playing the game is 12,400 with a standard deviation of 1500. During the same period, Jill's mean score is 14,200, with a standard deviation of 2000. They devise a fair contest: each one will play the game once, and they will compare z-scores. Jack gets a score of 14,000, and Jill gets a score of 16,000. Who won the contest, and what were each of their z-scores?

Jack's z = 1.07; Jill's z = 0.90; Jack wins the contest

A data set is Normally distributed with a mean of 25 and a standard deviation of 8. If you calculate the standard score of every observation in this data set, what will the mean and standard deviation of the resulting scores be?

Mean = 0; Standard deviation = 1

The Normal curve below describes the death rates from heart disease per 100,000 people in developed countries in the 1990's.

Mean ≈ 190; Standard Deviation ≈ 65

If the values in a data set are in feet, then what are the units for standard scores?

Standard scores do not have units.

The plot shown below is a Normal probability plot for the total annual cost (tuition plus room and board) to attend 126 of the top colleges in the country in 2005. Which statement is true for these data?

The data are clearly skewed to the left.

When a basketball player makes a pass to a teammate who then scores, he earns an "assist." Below is a Normal probability plot for the number of assists earned by all players in the National Basketball Association during the 2010 regular season. Which of the following statements about the shape of this distribution is true?

The distribution is skewed.

For the distribution whose density curve is shown below, defined on the interval 0 < x < 2, which of the following statements is true?

The mean is less than the median

A sample was taken of the salaries of 20 employees of a large company. The following are the salaries (in thousands of dollars) for this year. For convenience, the data are ordered. 28 31 34 35 37 41 42 42 42 47 49 51 52 52 60 61 67 72 75 77 Suppose each employee in the company receives a $3,000 raise for next year (each employee's salary is increased by $3,000).Use Scenario 2-1. The interquartile range of the salaries for the employees will

be unchanged

Scenario 2-1A sample was taken of the salaries of 20 employees of a large company. The following are the salaries (in thousands of dollars) for this year. For convenience, the data are ordered. 28 31 34 35 37 41 42 42 42 47 49 51 52 52 60 61 67 72 75 77 Suppose each employee in the company receives a $3,000 raise for next year (each employee's salary is increased by $3,000).Use Scenario 2-1. The z-scores of the salaries for the employees will

be unchanged.

A stemplot of a set of data is roughly symmetric, but the data do not even approximately follow the 68-95-99.7 rule. We conclude that the data are

not Normal

A score's percentile is a measure of

relative location

If 30 is added to every number on a list, which one of following does not change?

the standard deviation.