Statistics Quiz # 12

If the probability of getting a z-score between the mean of +1 standard deviation is 0.3413, what is the probability of getting a z-score of +1 standard deviation or less?

0.3413

0.1587

0.6587

0.8413

If the shape of a frequency distribution is lopsided, with a long tail projecting longer to the left than to the right, how would the distribution be skewed?

Normally

Negatively

Positively

Average

A z score is a standard score with a:

M = 2 and SD = -1

M = 0 and SD = 0

M = 0 and SD = 1

M = 1 and SD = 0

When a z-score is NOT in the region of rejection, we should ______.

Reject the idea that random chance produced a sample the represents the population poorly

Conclude with the idea that the sample scores and the raw score population are similar enough to be called identical

Not reject the idea that the sample represents the raw score population

Reject the idea that the sample represents the raw score population

When a z-score is NOT in the region of rejection, we should ______.

Reject the idea that random chance produced a sample the represents the population poorly

Conclude with the idea that the sample scores and the raw score population are similar enough to be called identical

Not reject the idea that the sample represents the raw score population

Reject the idea that the sample represents the raw score population

Faculty in the psychology department at State University consumes an average of 5 cups of coffee per day with a standard deviation of 1.5. The distribution is normal. What is the percentile rank for an individual who consumed 8 cups of coffee per day?

97.72

2.28

47.72

None of these

If the shape of a frequency distribution is lopsided, with a long tail projecting longer to the right than to the left, how would the distribution be skewed?

Normally

Negatively

Positively

Average

What percentage of scores falls within three standard deviation of the mean?

99.5%

50%

95%

65%

Faculty in the psychology department at State University consume an average of 5 cups of coffee per day with a standard deviation of 1.5. The distribution is normal. What proportion of faculty consumes an amount between 4 and 6 cups?

0.5468

0.4972

0.50

None of these

A Type I error occurs when we say that something ______.

Works when it really does

Doesn’t work when it really does

Works when it really doesn’t

Doesn’t work when it really doesn’t

Rejecting H0 when we should have failed to reject it is a ______ error.

Type I

Type II

Null

One-tailed

When the probability of a Type I error is less than .05, we say that we have observed ______.

A Type II error

Statistical significance

The alternative hypothesis

All of these

Which of the following accurately defines a Type I error?

Rejecting a null hypothesis when it is true

Retaining a null hypothesis when it is true

Rejecting a null hypothesis when it is false

Retaining a null hypothesis when it is false

The power of a statistical test is the probability of ______.

Failing to reject a false

Rejecting a false

Failing to reject a true

Rejecting a true

Failing to reject H0 when we should have rejected it is a ______ error.

Type I

Type II

Null

One-tailed

If researchers report that the results from their study were significant, p < 0.05, this means that ______.

If they conducted the study over, they would get the same results less than 5 times in 100

The results are untrustworthy

We would expect the results to occur by chance less than 95 times out of 100

We would expect the results to occur by chance less than 5 times out of 100

Which of the following accurately defines a Type II error?

Rejecting when it is true

Failing to reject when it is true

Rejecting when it is false

Failing to reject when it is false

What does it mean when a computer printout reads “p = 0.03”?

The result falls in the extreme 3% of the sampling distribution and the probability of a Type I error is 0.03.

The result falls in the extreme 3% of the sampling distribution and the probability of a Type II error is 0.03.

The probability of a Type I error (0.03) is smaller than α (0.05), and, therefore, the results are nonsignificant.

The probability of an error should be reported as p < 0.01.

Which of the following tests is considered more powerful?

A one-tailed test

A two-tailed test

Neither; they are both equally statistically powerful

Which is more powerful depends on the sample size

If you reject the null hypothesis, which of the following may occur?

A correct decision or a Type I error

A Type I error or a Type II error

A correct decision or a Type II error

A correct decision or a Type I error or a Type II error

Power is equal to ______.

The value of the Type II error subtracted from 1

The value of Type I error subtracted from 1

1 subtracted from the value of the Type II error

1 subtracted from the value of the Type I error

What happens to the probability of committing a Type I error if the level of significance is changed from alpha = 0.01 to alpha = 0.05?

The probability of committing a Type I error will decrease.

The probability of committing a Type I error will increase.

The probability of committing a Type I error will remain the same.

The change in probability will depend on your sample size.

What is the standard error of the mean for a distribution of scores where standard deviation for the population = 50 and the size of the sample = 75?

5.77

0.066

1.5

Unable to determine

The standard deviation of the sampling distribution is called the ______.

Standard deviation

Deviation of the sample

Standard error of the mean

Standard error of the population

What is the purpose of the critical value?

To determine the size of the region of rejection

To determine the maximum allowable population standard deviation

To determine the likelihood that the population mean was obtained by chance

To determine the value of z needed to conclude that the population mean was obtained by chance.

What is the standard error of the mean for a distribution of scores where the standard deviation for the population = 15 and the size of the sample = 100?

0.15

1.5

15

Unable to determine

The standard error of the mean will always be ______ the standard deviation for a distribution of individual scores.

Smaller than

Larger than

The same as

The same as or larger than

When can the z-test be used in statistical hypothesis testing?

When the measure of central tendency used for the raw scores is the median

When the raw scores are transformed from a nominal scale to a ratio scale

When the raw score population’s standard deviation is known

When the z-test standard deviation is known

If the obtained value is higher than the critical value, we ______.

Reject the null hypothesis

Accept the null hypothesis

Reject the research hypothesis

Cannot determine

What is the standard error of the mean for a distribution of scores where standard deviation for the population = 24 and the size of the sample = 144?

20

0.167

2.0

Unable to determine