HW Chapter 5

A scientist is interested in the effect of time spent with parents and the number of hours youth spend watching television. The researcher knows that the average teen whose parents work outside the home spends 20 hours a week watching television. The population mean = 20 and the standard deviation of the distribution is equal to 5. Calculate the z-scores for the following individual times: If X = 5, z = __________.

-3.0

The probability of rolling a '4' on one toss of a standard six-sided die AND a '6' on a second toss is:

.028

The probability of rolling a '4' on one toss of a standard six-sided die is:

.167

The probability of a student correctly guessing the answer to this question is:

.25

The probability of rolling a '4' OR a '6' on one toss of a standard six-sided die is:

.333

If 68% of IQ scores are between 85 and 115, what is the probability of meeting a person in the population within that IQ range?

.68

A scientist is interested in the effect of time spent with parents and the number of hours youth spend watching television. The researcher knows that the average teen whose parents work outside the home spends 20 hours a week watching television. The population mean = 20 and the standard deviation of the distribution is equal to 5. Calculate the z-scores for the following individual times: If X = 20, z = __________.

0.00

A scientist is interested in the effect of time spent with parents and the number of hours youth spend watching television. The researcher knows that the average teen whose parents work outside the home spends 20 hours a week watching television. The population mean = 20 and the standard deviation of the distribution is equal to 5. Calculate the z-scores for the following individual times: If X = 37, z = __________.

3.40

Roughly __________ of the total area under the normal curve rests between the mean and one standard deviation above.

34%

In a symmetrical distribution, what percent of the scores fall above the mean?

50%

Roughly __________ of the total area under the normal curve rests between two standard deviations above and below the mean.

95%

Which of the following is true of probabilities?

A probability varies from 0 to 1.0

Which of the following is true of the normal distribution?

All of the above: The normal distribution is symmetrical. The normal distribution is unimodal. The tails extend indefinitely in either direction.

A z score does NOT allow for the comparison of different scores from different distributions.

False

A z score tells nothing about the distance of a score from the mean.

False

About 75% of the scores in a normal distribution fall between the mean and three standard deviations above the mean.

False

Which of the following is NOT true of the normal curve?

It can be applied to any distribution encountered by a researcher.

Which of the following is NOT true of the normal curve?

It is skewed.

Probability is defined as:

P= number of times an outcome can occur/total number of times any outcome or event can occur

A number whose z score is equal to zero is equal to the mean.

True

Fifty percent of the scores fall below the mean in a normal curve.

True

A probability distribution has:

a mean and a standard deviation.

The normal curve is:

a theoretical ideal.

A normal curve:

all of the provided answers: is used in statistics for making decisions, can be used to describe distributions, and is a theoretical ideal or model.

About 95% of the scores in a normal distribution lie between two standard deviations below the mean AND two standard deviations above the mean.

true