Quiz 4 - Chapter 5 & 6

The variance of a distribution of means is smaller than the original population variance because

extreme scores are less likely to affect a distribution of means.

Effect size is an important tool for making sense of research results because it

indicates the size of the statistical effect.

The variance of a distribution of means of samples of more than one is

smaller than the original population variance.

Which of the following statistics would be the MOST likely to appear in a Research Article?

standard error

In actual practice, the usual reason for determining POWER before conducting a study is

to determine the number of participants needed to have a reasonable level of power.

When conducting an experiment with 95% power, failing to reject the Null Hypothesis means that

the chance that the data came from populations with a difference larger than that predicted when calculating power is less than 5%.

The item below is based on the following scenario. An experimental psychologist is interested in whether the color of an animal's surroundings affects learning rate. He tests 16 rats in a box with colorful wallpaper. The average rat (of this strain) can learn to run this type of maze in a box without any special coloring in an average of 25 trials, with a variance of 64, and a normal distribution. The mean number of trials to learn the maze, for the rats tested with the colorful wallpaper, is 11. If the mean score of the sample is more extreme than the cutoff score on the comparison distribution, the psychologist will conclude that

the color of the chamber had a significant effect on the rate of learning.

A 95% confidence interval is figured by finding

the cutoff points for the lower 2.5% and the upper 2.5% of the distribution.

Effect size is

the degree to which an experimental manipulation separates two populations

In hypothesis testing, after figuring the Z score for the sample's mean, the next step would be to compare this Z score to

the distribution of means that would be found if the null hypothesis were true.

Cohen's (1962) review of power in psychological studies revealed that

no study had power greater than 50%.

The item below is based on the following scenario. A manufacturer who is considering the implementation of a one-week training program for all new employees decides to test the program with the next 100 employees hired, and then compare their productivity rate to the productivity rate of new employees based on past records—a rate that is normally distributed with a mean of 60 and a standard deviation of 8. The new program needs to produce a minimum improvement of 4 to be considered worthwhile. What is the MEAN of the COMPARISON distribution?

60

A psychologist conducts a study and finds that d = -.63. This effect size would most likely be described as

medium

The item below is based on the following scenario. A large school district is considering implementing a program that, if successful, would improve the reading scores of its students by 10 points. The current reading scores for the district are normally distributed with a mean of 37 and a standard deviation of 12. The administrators decide to test the new program in one school of 340 students. What is the STANDARD DEVIATION of the COMPARISON DISTRIBUTION?

.65

The item below is based on the following scenario. A manufacturer who is considering the implementation of a one-week training program for all new employees decides to test the program with the next 100 employees hired, and then compare their productivity rate to the productivity rate of new employees based on past records—a rate that is normally distributed with a mean of 60 and a standard deviation of 8. The new program needs to produce a minimum improvement of 4 to be considered worthwhile. What is the comparison distribution's standard deviation?

0.80

The item below is based on the following scenario. Anxiously-attached individuals in the general population tend to have low levels of satisfaction in their romantic relationships (μ = 10, σ = 5, positively skewed distribution). A therapist interested in increasing relationship satisfaction provides a week-long relaxation seminar to 11 anxious individuals. After completing the seminar, relationship satisfaction in the sample averages 12. What is the corresponding Z score for the sample's mean score on the comparison distribution?

1.32

The item below is based on the following scenario. Anxiously-attached individuals in the general population tend to have low levels of satisfaction in their romantic relationships (μ = 10, σ = 5, positively skewed distribution). A therapist interested in increasing relationship satisfaction provides a week-long relaxation seminar to 11 anxious individuals. After completing the seminar, relationship satisfaction in the sample averages 12. What is the comparison distribution's standard deviation?

1.51

The item below is based on the following scenario. An experimental psychologist is interested in whether the color of an animal's surroundings affects learning rate. He tests 16 rats in a box with colorful wallpaper. The average rat (of this strain) can learn to run this type of maze in a box without any special coloring in an average of 25 trials, with a variance of 64, and a normal distribution. The mean number of trials to learn the maze, for the rats tested with the colorful wallpaper, is 11. What is the μM?

25

Your sample of 12 people is being compared to a known population with a mean of 200 and a variance of 36. What is the variance of the distribution of means?

3.00

The item below is based on the following scenario. A large school district is considering implementing a program that, if successful, would improve the reading scores of its students by 10 points. The current reading scores for the district are normally distributed with a mean of 37 and a standard deviation of 12. The administrators decide to test the new program in one school of 340 students. What is the MEAN of the COMPARISON DISTRIBUTION?

37

The item below is based on the following scenario. A large school district is considering implementing a program that, if successful, would improve the reading scores of its students by 10 points. The current reading scores for the district are normally distributed with a mean of 37 and a standard deviation of 12. The administrators decide to test the new program in one school of 340 students. What is the MEAN of the Comparison Distribution?

37

The item below is based on the following scenario. A large school district is considering implementing a program that, if successful, would improve the reading scores of its students by 10 points. The current reading scores for the district are normally distributed with a mean of 37 and a standard deviation of 12. The administrators decide to test the new program in one school of 340 students. What is the predicted mean of the Experimental Distribution?

47

Which of the following statements regarding confidence intervals is FALSE?

Confidence intervals are misused more often than significance tests.

The probability of NOT making a TYPE II ERROR is

POWER

A CHILD psychologist conducts a study to test whether infants born prematurely begin to walk earlier than do infants in general. Which of the following scenarios represents a TYPE II Error?

The psychologist concludes that premature infants Do Not walk earlier than infants in general when the true situation is that they actually DO.

A cognitive psychologist tests whether memory for abstract ideas improves when the information is presented both verbally and visually. Which of the following scenarios represents a Type I error?

The psychologist concludes that memory does improve when the true situation is that it Does Not Improve.

A cognitive psychologist tests whether memory for abstract ideas improves when the information is presented both verbally and visually. Which of the following scenarios represents a TYPE II ERROR?

The psychologist concludes that memory does not improve when the true situation is that it does improve.

A child psychologist conducts a study to test whether infants born prematurely begin to walk earlier than do infants in general. Which of the following scenarios represents a Type I error?

The psychologist concludes that premature infants do walk earlier than infants in general when the true situation is that they actually do not.

When hypothesis testing with a sample of two or more, the formula for figuring your sample's score on the Comparison Distribution is

Z = (M - μM) / σM

Rejecting the null hypothesis when the research hypothesis is false is

a TYPE I error

Using the .01 level of significance means that, in the long run,

a Type I error occurs 1 time in 100.

Setting the significance level at .20 increases the chance of

a Type I error.

Setting the significance level cutoff at .10 instead of the more usual .05 increases the likelihood of

a Type I error.

The 99% confidence interval is the region in a group of scores that

a psychologist can be 99% confident includes the true population mean.

The probability of rejecting the null hypothesis when in fact it is true is

alpha

If a study conducted at the .05 significance level has 80% power

alpha = 5%, beta = 20%

The item below is based on the following scenario. A large school district is considering implementing a program that, if successful, would improve the reading scores of its students by 10 points. The current reading scores for the district are normally distributed with a mean of 37 and a standard deviation of 12. The administrators decide to test the new program in one school of 340 students. What is the shape of the comparison distribution?

approximately normal

As the number of people in a sample gets larger, the distribution of means

becomes a better approximation of the normal curve.

The first thing that needs to be done to compute the 95% confidence interval is to

calculate the standard error.

If beta equals 70%, then alpha

cannot be determined from information provided.

The item below is based on the following scenario. Anxiously-attached individuals in the general population tend to have low levels of satisfaction in their romantic relationships (μ = 10, σ = 5, positively skewed distribution). A therapist interested in increasing relationship satisfaction provides a week-long relaxation seminar to 11 anxious individuals. After completing the seminar, relationship satisfaction in the sample averages 12. What is the shape of the comparison distribution?

cannot be determined from the information provided

The comparison distribution for the mean of a sample is the distribution of means because

comparing the mean of a sample to a distribution of a population of scores of individuals is a mismatch.

While no research hypothesis is ever definitely false, failing to reject the null hypothesis in a study that has a high level of power allows one to

conclude that the research hypothesis is most likely false.

The upper and lower ends of a confidence interval are the

confidence limits.

Cohen proposed effect-size conventions based on the effects observed in psychology research in general because

determining how large an effect can be expected in a given experiment is difficult.

Standard power tables are useful for

directly determining the power of an experiment.

Some psychologists have argued that simple significance tests are misleading, and that a better statistic to evaluate the outcome of an experiment would be the

effect size.

When the standard deviation of the original population is small, the experiment tends to

have a higher level of power.

Power is the probability that

if the research hypothesis is true, the experiment will support it.

A Type I error is the result of

incorrectly rejecting the null hypothesis.

The standard deviation of a distribution of means is sometimes called "the standard error of the mean," or the "standard error," because

it represents the degree to which particular sample means are "in error" as estimates of the mean of the population of individual scores.

A psychologist conducts a study and finds that d = 1.41. This effect size would most likely be described as

large

The mean and variance of a comparison distribution that would be used to test the hypothesis that the mean obtained in a study involving 10 participants is different from a known population having a mean of μ = 100 and σ2 = 25 would be

mean = 100, variance = 2.5

Which of the following would usually be considered "marginally significant"?

p .10

The effect size and the number of participants are two important determinants of

power

In principal, a distribution of means can be formed by

randomly taking a very large number of samples from a population, each of the same size, and making a distribution of their means.

The degree to which the experimental manipulation separates the two populations of individual scores is

the effect size.

The alpha level is

the probability of a Type I error.

If the research hypothesis is true but the study has a low level of power, then

the probability that the study will have a significant result is low.

The mean of a distribution of means is

the same as the original population mean.

Effect size is one of the two major factors that contribute to power; the other factor is

the sample size.

If an experimenter CANNOT Manipulate the effect size of an experiment to increase power, the aspect of a study that can usually be changed easily to Increase Power is

the sample size.

The standard deviation of a distribution of means is

the square root of the variance of the distribution of means.

Supporters of accepting results that reach only "marginal significance" argue that

the standard .05 significance level is an arbitrary convention.

Dividing the variance of the population of individuals by the number of individuals in each sample yields

the variance of the distribution of means.

One important advantage of using effect sizes is that

they are standardized scores that make comparisons of different studies easier.

Type II errors concern psychologists because

they could mean that good theories or useful practical procedures are not used.

In general, the shape of a distribution of means tends to be

unimodal and symmetrical.

James asks his friend Rob for advice on how to increase the power of his experiment. Which of Rob's suggestions is Incorrect?

use a two-tailed instead of a one-tailed test

The item below is based on the following scenario. An experimental psychologist is interested in whether the color of an animal's surroundings affects learning rate. He tests 16 rats in a box with colorful wallpaper. The average rat (of this strain) can learn to run this type of maze in a box without any special coloring in an average of 25 trials, with a variance of 64, and a normal distribution. The mean number of trials to learn the maze, for the rats tested with the colorful wallpaper, is 11. The SHAPE of the DISTRIBUTION of means

will be approximately normal.

The item below is based on the following scenario. An experimental psychologist is interested in whether the color of an animal's surroundings affects learning rate. He tests 16 rats in a box with colorful wallpaper. The average rat (of this strain) can learn to run this type of maze in a box without any special coloring in an average of 25 trials, with a variance of 64, and a normal distribution. The mean number of trials to learn the maze, for the rats tested with the colorful wallpaper, is 11. The Shape of the Distribution of Means

will be approximately normal.

The 95% confidence interval

will be narrower than the 99% confidence interval.

The difference between creating a Z score from a single score and creating one from a sample mean is that

you use the mean and standard deviation from the distribution of means.

The item below is based on the following scenario. An experimental psychologist is interested in whether the color of an animal's surroundings affects learning rate. He tests 16 rats in a box with colorful wallpaper. The average rat (of this strain) can learn to run this type of maze in a box without any special coloring in an average of 25 trials, with a variance of 64, and a normal distribution. The mean number of trials to learn the maze, for the rats tested with the colorful wallpaper, is 11. WHAT IS σM?

√(64/16) = 2.00