Interpret Standard Deviation AP Stats

On average, a randomly selected baby's apgar score will differ from the mean 8.128 by about 1.4 units.
This represent what?

• Interpret Standard deviation

• Interpret r

• Interpret r^2

• Interpret LSRL "yhat"

Terrina calculated her z-score for a recent test after the teacher provided the mean and standard deviation. It was 0.75. Interpret this z-score

• Terrina scored 0.75 standard deviations above the mean

• Terrina did as well or better than 75% of the students who took the test

• Terrina did as well or worse than 75 of the students who took the test

• Terrina scored 0.75 standard deviations below the mean.

What is true after standardizing data into z-scores.

• There is no change to the center

• The mean is 1 and the standard deviation is 0

• The mean is 0 and the standard deviation is 1

• There is no change to the range

A random variable X has a mean of 120 and a standard deviation of 15. A random variable Y has a mean of 100 and a standard deviation of 9. If X and Y are independent, approximately what is the standard deviation of X – Y?

• 24.0

• 17.5

• 12.0

• 6.0

• 4.9

A marketing survey compiled data on the number of personal computers in households. If X = the number of computers in a randomly-selected household, and we omit the rare cases of more than 5 computers, then X has the given distribution. The standard deviation of X is 1.27. Interpret this value.

• The number of computers in a randomly selected household is within 1.27 of the mean.

• The number of computers in a randomly selected household is exactly 1.27 from the mean.

• The number of computers in a randomly selected household is 1.27, on average.

• The number of computers in a randomly selected household is typically 1.27 from the mean.

• The average number of computers in a randomly selected household is typically 1.27 from the mean.

All of the below sets have the same mean.

Set 1-Standard Deviation=3.1

Set 2-Standard Deviation=4.9

Set 3-Standard Deviation=1.7

Set 4-Standard Deviation=3.2

Which set of data probably has the points closest to the mean?

• 2

• 4

• 3

• 1

A large corporation has thousands of employees. The distribution of annual salaries for the employees is skewed to the right, with a mean of $68,000 and a standard deviation of $18,000. Because business has been good this year, the CEO of the company decides that every employee will receive a $5000 bonus. Let X be the current annual salary of a randomly selected employee before the bonus and Y be the employee’s salary after the bonus. Describe the shape, center, and variability of the probability distribution of Y.

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The average high temperature in July for a midwest city is 89 degrees. What is the standard deviation if 15% of July's on record for the city have an average high temperature above 91.5 degrees? Assume average temperatures are normally distributed.

• s = 0.060

• s = 16.667

• s = 0.416

• s = 2.404

95% of students who take the AP stats exam need between 186 and 214 minutes to complete it. What is the standard deviation of time students need to finish the exam? Assume times are normally distributed.

• 4.67 minutes

• 14 minutes

• 7 minutes

• 28 minutes

Suppose that the mean of a set of values is 20, and the standard deviation is 3. If each value is increased by 5, what will be the mean and standard deviation of the new set of values?

• mean = 25, sd = 8

• mean = 20, sd = 3

• mean = 20, sd = 8

• mean = 25, sd = 3