midterm apstats review

A sample of production records for an automobile manufacturer shows the following figures for production per shift:

d. (50.00)

Use Scenario 1-3. Based on this histogram, the percentage of the winning jumps that were at least 80 inches is about

d. (55%.)

Use Scenario 1-7. The number of children with birth weights between 102 and 122 ounces is approximately:

d. (80)

Which of the following descriptions best fits this distribution?

d. (Roughly symmetric, centered at about 150, range 80)

The risk of an investment is measured by the variability of the changes in its value over a fixed period, such as a year. More variation from year to year means more risk. The government's Securities and Exchange Commission wants to require mutual funds to tell investors how risky they are. A New York Times article says that some people think that "the proposed risk descriptions, especially one that goes by the daunting name standard deviation" are hard to understand. Explain to a friend what the standard deviation means, using the fact that the changes in a mutual fund's value over many years have a roughly Normal distribution.

d. (Start with the average (mean) change in the fund's value over many years; the actual change will be within one standard deviation of that average in about 68% of all years.)

Based on the graphs, which one of the following statements must be true?

d. (The median word length for Rowling is longer than for either Starnes or James.)

The five-number summary of the distribution of scores on the final exam in Psych 001 last semester was: 18 39 62 76 100. Which of the following best describes the location of the 80th percentile?

d. (between 76 and 100)

Using the standard Normal distribution tables, the area under the standard Normal curve corresponding to Z < 1.1 is

e. (0.8643.)

Using the standard Normal distribution tables, the area under the standard Normal curve corresponding

e. (0.8888.)

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

e. (102 and 118.)

Use Figure 2-1. For this density curve, what percent of the observations lie between 0.2 and 3.8?

e. (72%)

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

e. (All of the above.)

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?

e. (Mean = 0; Standard deviation = 1)

Use Scenario 1-7. The median birth weight is approximately

d. (110 ounces)

What percent of the schools have an acceptance rate of under 20%?

d. (16%)

Use Scenario 1-5. The interquartile range for the number of A.P. Courses is

d. (2)

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.?

a. (0.160)

The mean undergraduate IQ is 110. About 95% of undergraduates have IQs between 100 and 120. The standard deviation of these IQs is about

a. (5.)

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 between 125 oz. and 140 oz.?

a. (0.135)

Use Scenario 1-3. Which of the following values is closest to the mean jump?

d. ( 81 inches.)

Using the standard Normal distribution tables, the area under the standard Normal curve corresponding to -0.5 < Z < 1.2 is

d. (0.5764.)

The first sentence in Henry James's novel The Turn of the Screw has 62 words. The five number summary for the lengths of those words is 1, 2, 3.5, 6, 12. According to the 1.5 x IQR rule for identifying outliers, does this distribution have any outliers?

a. (No, there are no outliers.)

Use Scenario 1-4. This stemplot is most similar to

a. (a histogram with class intervals 110 £ score < 120, 120 £ score < 130, etc.)

Use Scenario 2-1. Use Scenario 2-1. The standard deviation of the salaries for the employees will

a. (be unchanged.)

You can roughly locate the mean of a density curve by eye because it is

a. (the point at which the curve would balance if made of solid material.)

The mean number of days that the midge Chaoborus spends in its larval stage is 14.1 days, with a standard deviation of 2.2 days. This distribution is skewed toward higher values. What is the z-score for an individual midge that spends 12.7 days in its larval stage?

b. (-0.64)

According to the 1.5 x IQR rule, which values in the above distribution are outliers?

b. (14 only)

The standard deviation of 16 peoples' weights (in pounds) is computed to be 5.4. The variance of these measurements is

b. (29.16.)

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?

b. (31.85)

All of the following distributions have a mean of 10. Which has the largest standard deviation?

b. (5,5,5,15,15,15)

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

b. (65% of the population scores are above x.)

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?

b. (78.4 minutes)

Use Scenario 1-5. Which of the following is a correct box plot for these data?

b. (B)

Which of the following statements is true?

b. (Fifty percent of the scores in a distribution are between the first and third quartile.)

A statistics teacher asks the 29 students in his statistics class how many minutes they spent on one homework assignment. The distribution of the variable "time on homework" is

b. (a description of what values the variable takes and how often it takes them.)

Use Scenario 2-1. The mean salary for the employees will

b. (increase by $3,000.)

Use Scenario 2-1. The median salary for the employees working for the company will

b. (increase by $3,000.)

There are three children in a room, ages three, four, and five. If another four-year-old child enters the room the

b. (mean age will stay the same but the variance will decrease.)

You can roughly locate the median of a density curve by eye because it is

b. (the point that divides the area under the curve into two equal parts.)

The five number summary for these data is:

c. (0, 6.5, 11, 28.5, 48)

The distribution of household incomes in a small town is strongly skewed to the right. The mean income is $42,000 and the standard deviation is $24,000. The Ames family's household income is $60,000. The z-score for the Ames family's income is

c. (0.75)

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?

c. (310)

The mean and standard deviation of this distribution are approximately

c. (Mean a 190; Standard Deviation a 65)

For the distribution whose density curve is shown below, defined on the interval 0 ?4= x ?4= 2, which of the following statements is true?

c. (The mean is less than the median)

Use Scenario 1-6. Based on the boxplot, which of the following statements is true?

c. (The range of the middle half of the salaries is about $20,000)

A particularly common question in the study of wildlife behavior involves observing confrontations between "residents" of a particular area and "intruders." In each contest, the "residents" either win or lose the encounter (assuming there are no ties). Observers might record several variables, listed below. Which of these variables is categorical?

c. (Whether the "residents" win or lose.)

X and Y are two categorical variables. The best way to determine if there is a relation between them is to

c. (make a two-way table of the X and Y values.)

The standard deviation of 16 peoples' weights (in pounds) is computed to be 5.4. The units for the variance of these measurements is

c. (pounds squared.)

A score's percentile is a measure of

c. (relative location)