AP Stats Inferences for Means

What would you expect the correlation between study time and test grades to be?

• close to 1

• close to -1

• 0

• cannot be determined

If no alpha level is given, what alpha level is assumed?

• 0.01

• 0.10

• 0.25

• 0.05

A machine at a manufacturing company is programmed to fill shampoo bottles such that the amount of shampoo in each bottle is normally distributed with mean 0.60 liter and standard deviation 0.04 liter. Let the random variable A represent the amount of shampoo, in liters, that is inserted into a bottle by the filling machine. A bottle is considered underfilled if it has less than 0.50 liter of shampoo. Determine the probability that a randomly selected bottle of shampoo will be underfilled. 

• .9938

• .0062

• -2.5

• none of these

The most important condition for making an inference about a population mean from a significance test is that

• the data comes from a radom sample

• the population distribution is exactly normal

• the data contains no outliers

• the sample size is less than 10% of the population

• the sample size is at least 30

• A

• B

• C

• D

• E

Which of the following is a true statement?

• The larger the sample, the larger the spread in the sampling distribution.

• Bias has to do with the spread of a sampling distribution. 

• Provided that the population size is significantly greater than the sample size, the spread of the sampling distribution does not depend on the population size.

• Sample parameters are used to make inferences about population statistics.

In a school of 2500 students, the students in an AP Statistics class are planning a random survey of 100 students to estimate the proportion who would rather drop lacrosse rather than band during this time of severe budget cuts. Their teacher suggests instead to survey 200 students in order

• reduce bias.

• reduce variability.

• increase bias.

• increase variability.

A quality control specialist at a glass factory must estimate the mean clarity rating for a new batch of glass using a sample of 18 glass sheets from the batch. Past investigations show that clarity ratings are normally distributed. The specialist decides to use a t-distribution rather than a z-distribution because ...

• The t distribution is more accurate than a z distribution.

• Clarity ratings for the entire batch are normally distributed.

• The t-distribution will create a narrower interval than z.

• The standard deviation for the population is unknown.

Thirty randomly selected students took the calculus final. If the sample mean was 92 and the standard deviation was 9.4, construct a 99 percent confidence interval for the mean score of all students from which the sample was gathered.

• 89.08 < μ < 94.92

• 87.27 < μ < 96.73

• 87.29 < μ < 96.71

• 87.77 < μ < 96.23

A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of 45 CEOs. The interval was $139,048 to $154,144. Give the interpretation of the interval.

• 90% of the sampled CEOs have salaries that fell in the interval $139,048 to $154,144

• We are 90% confident that the mean salary of all CEOs in the electronics industry falls in the interval $139,048 to $154,144.

• There is a 90% chance that CEOs in the electronics industry have salaries that fall between $139,048 to $154,144

• We are 90% confident that the mean salary of the sampled CEOs falls in the interval $139,048 to $154,144.