Exam 2 BESC Final

What is one important difference between a point estimate and a confidence interval?

A point estimate gives a single value but a confidence interval gives a range of values

For which measures is it possible to compute a confidence interval?

Any population parameter

Which measure requires a degrees of freedom calculation?

sample standard deviation

Imagine a sample with n = 225 and a mean of 23 that comes from a population with a standard deviation of 30. Based on these data, what would be the 90% confidence interval for the population mean? (Use z-scores of ±1.64 for the 90% confidence level.)

(19.72, 26.28)

Imagine a sample with n = 16 and a mean of 52 that comes from a population with a standard deviation of 12. Based on these data, what would be the 95% confidence interval for the population mean? (Use z-scores of \pm ±±1.96 for the 95% confidence level.)

(46.12, 57.88)

Imagine a sample with n = 64 and a mean of 72 that comes from a population with a standard deviation of 24. Based on these data, what would be the 99.9% confidence interval for the population mean? (Use z-scores of ±3.29 for the 99.9% confidence level.)

(62.13, 81.87)

Imagine a sample with n = 49 and a mean of 95 that comes from a population with a standard deviation of 14. Based on these data, what would be the 80% confidence interval for the population mean? (Use z-scores of ±1.28 for the 80% confidence level.)

(92.44, 97.56)

If a test has a population mean of 140 and standard deviation of 12, then what is the z-score for the sample of n = 9 scores with a mean of 136?

-1

When choosing a level of alpha for a hypothesis test, unless you have a compelling reason to do otherwise, you should use...

.05

If a positively skewed distribution of 132 scores with a mean of 49 and a standard deviation of 14 is standardized then the new distribution's mean will be ______.

0

What is the standard error of a distribution if σ= 10 and n = 100?

1

If a distribution has a mean of 20 and a standard deviation of 3, then a raw score of 26 would have a z-score of ______.

2

If a distribution has a mean of 200 and a standard deviation of 40, then what is the standard error for a sample of 400 scores?

2

If a distribution has a mean of 70 and a standard deviation of 4, then what is the z-score for a sample of 64 scores with a mean of 71?

2

If a population has a mean of 40 and a standard deviation of 9, what would the z-score be for a sample of 9 people with a mean of 46?

2

What is the population variance for this data set? 4, 1, 2, 5

2.5

If a population has a mean of 60 and a standard deviation of 8, what is the z-score for a sample of 144 people with an average of 62?

3

If the population mean for a distribution is 150 and the standard deviation is 10, then what is the z-score for a sample of 100 people with an average score of 153?

3

What is the sample standard deviation for this data set? 4, 1, 9, 1, 5

3.32

What is the point estimate for the population mean if the sample mean is 55, the population standard deviation is 15, and the sample size is 25?

55

What is the IQR for this data set? 8, 1, 1, 3, 1, 8, 4, 7

6.5

What is meant by a "manipulation" in the context of experimental research?

Any variable that is controlled by the researcher

A bar chart would work best for which of the following measurement scales?

Categorical levels

If you conduct a one-sample z-test, you would test...

The null hypothesis of no difference between the group's mean and the population mean.

Imagine two samples that are drawn from the same population and measure the same variables in the same way. Sample A has a narrower confidence interval than Sample B does. Which sample likely has the larger n?

Sample A

Imagine two studies that are identical in every respect except the size of their samples. Sample A has an effect size of d = .50 and a p-value of .07. Sample B has an effect size of d = .50 and a p-value of .04. Which sample likely had the smaller sample size?

Sample A

Imagine two studies that are identical in every respect except their p-values and effect sizes. Sample A has a sample size of n = 60 and a p-value of .02. Sample B has a sample size of n = 60 and a p-value of .08. Which sample likely had the larger effect size?

Sample A

Imagine that two samples - Sample A with n = 10 and Sample B with n = 50 - are drawn from the same population and confidence intervals are computed for the same variables, which sample will have the narrower confidence interval?

Sample B

What does it mean when the result of a z-test is called "statistically significant"?

The alpha value was greater than the p-value

Which is more precise: a point estimate or a confidence interval?

a point estimate

When a sample comes randomly from the general population but that sample's mean is nonetheless significantly different from the population's, then...

a Type I error has occurred

Which is more accurate: a point estimate or a confidence interval?

a confidence interval

A sampling distribution can be calculated for...

any sample statistic

If a distribution of raw scores is completely uniform, then, given a sufficiently large n, the sampling distribution of means for that distribution will...

be normal

When the range of confidence for a confidence interval becomes lower - from 95% to 90%, for example - then the confidence interval will...

become narrower

When the standard deviation increases, the confidence interval will...

become wider

Imagine that a researcher is interested in whether students who receive an experimental teaching method have higher standard test scores than the national average. What would be an appropriate alternate hypothesis for a one-tailed or directional z-test for this test?

experimental students' average > national average

Assuming that the null hypothesis is actually false, then what is the easiest way to make sure that it will be rejected?

increase n

In statistics, "estimation" refers to using sample data to...

infer a population parameter.

What is the lowest level of measurement needed to calculate the mean?

interval

A histogram is appropriate when the data are...

interval or ratio

In a one-tailed or directional test for a one-sample z-test, if the observed value of z is greater than the critical value of z, then the null hypothesis...

is rejected

When n increases, what happens to a confidence interval?

it becomes narrower

Data is generally gathered from samples instead of populations because...

it may be impossible to gather data from populations.

A confidence interval specifies a range of values for a parameter estimate, whereas a point estimate specifies...

just a single value for that parameter.

If you want to use a one-sample z-test, you must first...

know the population standard deviation

Which measure of central tendency works best of negatively skewed distributions?

median

A bell curve (i.e., a normal distribution) is...

mesokurtic

In a negatively skewed distribution, which measure will generally have the highest value?

mode

If a person's employment is coded as Unemployed = 0 or Employed = 1, then that variable is at the ______ level of measurement.

nominal

The lowest level of measurement (i.e., the one that contains the least information) is the ______ level of measurement.

nominal

What is the lowest level of measurement needed to calculate the mode?

nominal

If a researcher conducts a z-test and does not reject the null hypothesis, then...

none of the other choices is correct

As the size of samples (n) in a sampling distribution increases, the shape of that distribution becomes more...

normal

The Central Limit Theorem states that as the number of sample means in the distribution increases, the shape of a sampling distribution becomes closer to a...

normal distribution

According to the central limit theorem, when all possible samples of a sufficient size are taken from a bimodal population and their means are charted, that distribution of means will be...

normally distributed

As n increases, the point estimate for the mean will...

not change

If you can use only one number to estimate a population parameter, then the best value is a...

point estimate

The number of small businesses opened in a county each year is an example of which level of measurement?

ratio

If a researcher is using an critical value of ±1.96 for a z-test and gets an observed (or test) z of -2.73, then the researcher should...

reject the null hypothesis

If a researcher is using an alpha of .05 for a z-test and gets an observed (or test) p-value of .06, then the researcher should...

retain (i.e., fail to reject) the null hypothesis.

According to the Central Limit Theorem, the mean of the sampling distribution of means -\mu_{\overline X}μX⎯⎯⎯⎯μX¯- will equal...

the mean of the original population

If you draw a picture of the null distribution with the critical values and regions of rejection marked, then the alpha level is represented by...

the proportion of the distribution in the regions of rejection.

If a researcher is using alpha = .05 and gets a p-value for the z-test of p = .02, then...

the results are unlikely to occur by chance if the null hypothesis is true.

A Type I error occurs when...

the sample data lead a researcher to reject a null hypothesis that is, in fact, true.

A Type II error occurs when...

the sample data lead a researcher to retain (i.e., fail to reject) a null hypothesis that is, in fact, false.

A point estimate for the population mean is based on...

the sample mean

If a researcher is comparing a sample mean to a population mean and gets Cohen's d = 0, this means that...

the sample mean is the same as the population mean.

When calculating an effect size for the z-test...

the sample size is irrelevant

The distribution of all possible sample means (of a given size) is called...

the sampling distribution of means

When the distribution of all possible samples of a given size are taken from a population and their means are charted, that distribution is known as...

the sampling distribution of means.

If a person were to create a sampling distribution for sample standard deviations, then the mean of that distribution would be equal to...

the standard deviation of the original distribution.

The standard error is...

the standard deviation of the sampling distribution

In order to calculate a one-sample z-test you need...

to know the population mean and variance/standard deviation.

If the formula for the population standard deviation were used with sample data, then result would be...

too small

If scores in a data set are very different from each other, then, compared to when they are more similar to each other, the standard deviation...

will be high