Take this Exam: AP Statistics — the four big ideas | Zestly

Question 1

Why is random assignment essential in a controlled experiment?

Accepted Answer

It tends to balance out the effects of lurking variables across treatment groups.

Answer

It ensures the sample is representative of the entire population.

Answer

It eliminates the need for a control group.

Answer

It allows the researcher to generalise the results to the entire population.

Question 2

A salesperson rings one household after another and records how many calls it takes to make the first sale. They want to model that count with a geometric distribution. Which condition must hold for the model to be appropriate?

Accepted Answer

Each call is independent of the others and the probability of a sale is the same on every call.

Answer

The number of calls must be fixed in advance, for example exactly twenty.

Answer

The probability of a sale must rise with each call, since the salesperson is getting practice.

Answer

Each call's outcome must depend on the outcome of the call before it.

Question 3

Adult reaction times in a large population are strongly right-skewed, with mean $\mu = 280$ milliseconds and standard deviation $\sigma = 60$ milliseconds. A researcher draws many random samples of $n = 100$ people and writes down the mean of each sample. Which statement describes the distribution of those recorded sample means?

Accepted Answer

Approximately normal, centred near 280 milliseconds, with standard deviation about 6 milliseconds.

Answer

Strongly right-skewed like the population, with standard deviation about 60 milliseconds.

Answer

Approximately normal, centred near 280 milliseconds, with standard deviation about 60 milliseconds.

Answer

Strongly right-skewed, centred near 280 milliseconds, with standard deviation about 6 milliseconds.

Question 4

From one sample, a researcher computes a 95 percent confidence interval for a population mean and gets 10 to 15. Which interpretation is correct?

Answer

There is a 95 percent probability that the true population mean lies between 10 and 15.

Answer

We are 95 percent confident that the interval from 10 to 15 captures the true population mean.

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About 95 percent of the individual values in the population lie between 10 and 15.

Answer

There is a 95 percent probability that a new sample would produce a mean between 10 and 15.

Question 5

In a hypothesis test, a p-value of 0.03 is obtained. Which of the following is the correct interpretation?

Answer

There is a 3% chance that the null hypothesis is false.

Answer

There is a 97% chance that the alternative hypothesis is true.

Answer

Assuming the null hypothesis is true, there is a 3% probability of observing a result as extreme as the one obtained.

Answer

The null hypothesis has been proven false.