Midterm

T/F For a sample with M = 10 and s = 2, a score of X = 13 would be considered an extreme score, far out in the tail of the distribution.

FALSE

A Type II error occurs when a researcher concludes that a treatment has an effect but, in fact, the treatment has no effect. T or F?

False

A researcher administers a treatment to a sample from a population with a mean of u = 60. If the treatment is expected to increase scores and a one-tailed test is used to evaluate the treatment effect, then the null hypothesis would state that u >/= 60. True or False?

False

A researcher is evaluating a treatment that is expected to increase scores. If a one-tailed test with a = .05 is used, then the critical region consists of z-scores less than -1.65. T or F?

False

If a hypothesis test leads to rejecting the null hypothesis, it means that the sample data failed to provide sufficient evidence to conclude that the treatment has an effect. T or F?

False

If a hypothesis test rejects the null hypothesis using an alpha level of a = .05, then the research report would include the statement, "p > .05". T or F?

False

If other factors are held constant, lowering the alpha level will increase the power of a hypothesis test. T or F?

False

If the sample data are in the critical region with a = .05, then the same sample data would still be in the critical region if a were changed to .01. T or F?

False

The null hypothesis states that the sample mean (after treatment) is equal to the original population mean (before treatment). T or F?

False

The power of a hypothesis test is the probability that the sample mean will be in the critical region even if the treatment has no effect. T or F?

False

For the following grouped frequency distribution table of exam scores, how many students had scores lower than X = 75? X f 95-99 | 6 90-94 | 3 85-89 | 4 80-84 | 5 75-79 | 2 70-74 | 1 a) 3 b) 2 c) 1 d) 6

NOT a) 3

When calculating the standard deviation, it is customary to round to _____ decimal point(s). a) 2 b) 1 c) 3 d) 4

NOT c) 3

What is the mode for the population of scores presented in the frequency distribution table below? X f 5 1 4 4 3 3 2 4 1 2 a) 3 b) 2 c) 4 d) 2 and 4

NOT c) 4

T/F In a population with a mean of µ = 30 and a standard deviation of σ = 5, a score of X = 18 would be an extreme value, far out in the tail of the distribution.

TRUE

If all other factors are held constant, increasing the sample size from n = 25 to n = 100 will increase the power of a statistical test. T or F?

True

If other factors are held constant, then increasing the sample size will increase the likelihood of rejecting the null hypothesis. T or F?

True

A Type I error occurs when a treatment has no effect but the decision is to reject the null hypothesis. T or F?

True

A Type II error occurs when a treatment actually does have an effect on the scores but the effect was not large enough to reject the null hypothesis. T or F?

True

Although the size of the sample can influence the outcome of a hypothesis test, it has little or no influence on measures of effect size. T or F?

True

If the power for a hypothesis test is calculated to be 0.80, then for same test, the probability of a Type II error is 0.20. T or F?

True

If the research prediction is that the treatment will decrease scores, then the critical region for a directional test will be in the left-hand tail. T or F?

True

If the sample data are in the critical region with a = .01, then the same sample data would still be in the critical region if a were changed to .05. T or F?

True

In a research report, p < .05 indicates that the probability of a Type I error is less than .05. T or F?

True

In a research report, the term significant result means that the null hypothesis was rejected. T or F?

True

In general, the null hypothesis states that the treatment has no effect on the population mean. T or F?

True

In most situations, researchers would like the hypothesis test to reject the null hypothesis. T or F?

True

It is possible for a very small treatment effect to be a statistically significant treatment effect. T or F?

True

T/F For the Empirical Rule, 95% of scores are within -2SD and +2SD.

True

T/F SS/N is the formula for population variance.

True

T/F Standard deviation squared = variance.

True

The alpha level determines the risk of a Type I error. T or F?

True

The critical region for a hypothesis test consists of sample outcomes that are very unlikely to occur if the null hypothesis is true. T or F?

True

The null hypothesis predicts a specific value for the population mean. T or F?

True

The value obtained for Cohen's d is independent of the sample size. T or F?

True

There is always a possibility that the decision reached in a hypothesis test is incorrect. T or F?

True

You can reduce the risk of a Type I error by using a larger sample. T or F?

True

For a population with µ = 84 and σ = 4, what is the z-score corresponding to X = 80? a) -1.00 b) +1.00 c) +1.25 d) -1.50

a) -1.00

What is the value of the median for the following set of scores? Scores: 1, 4, 6, 7, 9, 15, 15, 16, 25, 30 a) 12 b) 11 c) 15 d) 8

a) 12

What is z for the population? X = 34 μ = 26 σ = 4 a) 2 b) 4 c) 8 d) 6

a) 2

A sample of n = 12 scores ranges from a high of X = 7 to a low of X = 4. If these scores are placed in a frequency distribution table, how many X values will be listed in the first column? a) 4 b) 3 c) 12 d) 7

a) 4

If n = 20, what is k or the appropriate amount of groups? a) 5 b) 9 c) 7 d) 10

a) 5

What is the variance of the population when SS = 36, and N = 4? a) 9 b) 2 c) 7 d) 100

a) 9

Which of the following statements must be false regarding a distribution of scores? a) All of these statements are false. b) You can't have a mode in a set of scores. c) No individual has a score exactly equal to the mean. d) No individual has a score exactly equal to the median.

a) All of these statements are false.

Which of the following accurately describes a hypothesis test?

a) a descriptive technique that allows researchers to describe a sample b) a descriptive technique that allows researchers to describe a population c) an inferential technique that uses the data from a sample to draw inferences about a population* d) an inferential technique that uses information about a population to make predictions about a sample

If a treatment has a very small effect, what is a likely outcome for a hypothesis test evaluating the treatment?

a) a type I error b) a type II error* c) correctly reject the null hypothesis d) correctly fail to reject the null hypothesis

What is the relationship between the alpha level, the size of the critical region, and the risk of a Type I error?

a) as the alpha level increases, the size of the critical region increases, and the risk of a Type I error increases* b) as the alpha level increases, the size of the critical region increases, and the risk of a Type I error decreases c) as the alpha level increases, the size of the critical region decreases, and the risk of Type I error increases d) as the alpha level increases, the size of the critical region decreases, and the risk of a Type I error decreases

By selecting a larger alpha level, a researcher is ________.

a) attempting to make it easier to reject Ho b) better able to detect a treatment effect c) increasing the risk of a type I error d) all of the other options are the results of selecting a larger alpha level*

With a = .05, how are the boundaries for the critical region determined?

a) boundaries are drawn so there is 2.5% (.025) in each tail of the distribution* b) boundaries are drawn so there is 5% (.05) in each tail of the distribution c) boundaries are drawn so there is 10% (.10) in each tail of the distribution d) boundaries are drawn so there is 5% (.05) in the center of the distribution

Which of the following will increase the power of a statistical test?

a) change a from .05 to .01 b) change from a one-tailed test to a two-tailed test c) change the sample size from n = 25 to n = 100* d) none of the other options will increase power

What is the consequence of a Type I error?

a) concluding that a treatment has an effect when it really does b) concluding that a treatment has no effect when it really has no effect c) concluding that a treatment has no effect when it really does d) concluding that a treatment has an effect when it really has no effect*

What is the consequence of a Type II error?

a) concluding that a treatment has an effect when it really does b) concluding that a treatment has no effect when it really has no effect c) concluding that a treatment has no effect when it really does* d) concluding that a treatment has an effect when it really has no effect

A researcher evaluates a treatment effect using a two-tailed hypothesis test with a = .05, and the decision is to reject the null hypothesis. If the researcher switched to a one-tailed test using the same sample, what decision would be made?

a) definitely reject the null hypothesis with a = .05 and maybe reject with a = .01* b) definitely reject the null hypothesis with a = .05 and with a = .01 c) definitely fail to reject the null hypothesis with either a = .05 or with a = .01 d) it is impossible to predict the outcome of the one-tailed test

A researcher evaluates a treatment effect using a one-tailed hypothesis test with a = .05, and the decision is to reject the null hypothesis. If the researcher switched to a two-tailed test using the same sample, what decision would be made?

a) definitely reject the null hypothesis with either a = .05 or with a = .01 b) definitely reject the null hypothesis with a = .05 and maybe reject with a = .01 c) might reject the null hypothesis with a = .05 but might not* d) definitely fail to reject the null hypothesis with either a = .05 or with a = .01

For a hypothesis test evaluating the effect of a treatment on a population mean, what basic assumption is made concerning the treatment effect?

a) if there is a treatment effect, it will increase the scores b) if there is a treatment effect, it will decrease the scores c) if there is a treatment effect, it will add (or subtract) a constant to each score* d) if there is a treatment effect, it will multiply (or divide) each score by a constant

Which of the following correctly describes the effect of increasing the alpha level (for example, from .01 to .05)?

a) increase the likelihood of rejecting Ho and increase the risk of a Type I error* b) decrease the likelihood of rejecting Ho and increase the risk of a Type I error c) increase the likelihood of rejecting Ho and decrease the risk of a Type I error d) decrease the likelihood of rejecting Ho and decrease the risk of a Type I error

Which of the following accurately describes the effect of increasing the alpha level?

a) increases the standard error and has no effect on the risk of a type I error b) decreases the standard error and has no effect on the risk of a type I error c) increases the risk of a type I error and has no effect on the standard error* d) decreases the risk of a type I error and has no effect on the standard error

Which of the following accurately describes the effect of increasing the sample size?

a) increases the standard error and has no effect on the risk of a type I error b) decreases the standard error and has no effect on the risk of a type I error* c) increases the risk of a type I error and has no effect on the standard error d) decreases the risk of a type I error and has no effect on the standard error

What is the effect of decreasing the alpha level (for example, from a = .05 to a = .01)?

a) it decreases the probability of a type I error b) it decreases the size of the critical region c) it decreases the probability that the sample will fall into the critical region d) all of the other options are results of decreasing alpha*

Which of the following accurately describes the critical region?

a) outcomes with a very low probability if the null hypothesis is true* b) outcomes with a high probability if the null hypothesis is true c) outcomes with a very low probability whether or not the null hypothesis is true d) outcomes with a high probability whether or not the null hypothesis is true

Which term is used to describe the shape of a frequency distribution graph in which most scores pile up on the left-hand side of the graph and taper off to the right? a) positively skewed b) negatively skewed c) normal d) symmetrical

a) positively skewed

If a hypothesis test produces a z-score in the critical region, what decision should be made?

a) reject the alternative hypothesis b) fail to reject the alternative hypothesis c) reject the null hypothesis* d) fail to reject the null hypothesis

A two-tailed hypothesis is being used to evaluate a treatment effect with a = .05. If the sample data produce a z-score of z = -2.24, what is the correct decision?

a) reject the null hypothesis and conclude that the treatment has no effect b) reject the null hypothesis and conclude that the treatment has an effect* c) fail to reject the null hypothesis and conclude that the treatment has no effect d) fail to reject the null hypothesis and conclude that the treatment has an effect

Which of the following is an accurate definition of a Type II error?

a) rejecting a false null hypothesis b) rejecting a true null hypothesis c) failing to reject a false null hypothesis* d) failing to reject a true null hypothesis

Which of the following is an accurate definition of a Type I error?

a) rejecting a false null hypothesis b) rejecting a true null hypothesis* c) failing to reject a false null hypothesis d) failing to reject a true null hypothesis

A hypothesis test involves a comparison of which two elements?

a) research results from a sample and a hypothesis about a population* b) research results from a population and a hypothesis about a sample c) research results from a population and a hypothesis about the population d) research results from a sample and a hypothesis about the sample

Which of the following is directly addressed by the null hypothesis?

a) the population before treatment b) the population after treatment* c) the sample before treatment d) the sample after treatment

Which of the following is an accurate definition for the power of a statistical test?

a) the probability of rejecting a true null hypothesis b) the probability of supporting true null hypothesis c) the probability of rejecting a false null hypothesis* d) the probability of supporting a false null hypothesis

A sample of n = 25 individuals is selected from a population with u = 80, and a treatment is administered to the sample. What is the expected if the treatment has no effect?

a) the sample mean should be very different from 80 and should lead you to reject the null hypothesis b) the sample mean should be very different from 80 and should lead you to fail to reject the null hypothesis c) the sample mean should be close to 80 and should lead you to reject the null hypothesis d) the sample mean should be close 80 and should lead you to fail to reject the null hypothesis*

A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the null hypothesis (Ho) say about the treatment?

a) the treatment causes a change in the scores b) the treatment adds a constant to each score c) the treatment multiplies each score by a constant d) the treatment has no effect on the scores*

A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the alternate hypothesis (H1) say about the treatment?

a) the treatment causes a change in the scores* b) the treatment adds a constant to each score c) the treatment multiplies each score by a constant d) the treatment has no effect on the scores

When is there a risk of a Type II error?

a) whenever Ho is rejected b) whenever H1 is rejected c) whenever the decision is "fail to reject Ho"* d) the risk of a Type II error is independent of the decision from a hypothesis test

When is there a risk of a Type I error?

a) whenever Ho is rejected* b) whenever H1 is rejected c) whenever the decision is "fail to reject Ho" d) the risk of a Type I error is independent of the decision from a hypothesis test

You complete a hypothesis test using a = .05, and based on the evidence from the sample, your decision is to reject the null hypothesis. Which of the following is true?

a) you have made a type I error b) you have made a type II error c) you might have made a type I error, but the probability is less than 5%* d) you have made the correct decision

You complete a hypothesis test using a = .05, and based on the evidence from the sample, your decision is to reject the null hypothesis. If the treatment actually does have an effect, which of the following is true?

a) you have made a type I error b) you have made a type II error c) you might have made a type I error, but the probability is only 5% at most d) you have made the correct decision*

You complete a hypothesis test using a = .05, and based on the evidence from the sample, your decision is to fail to reject the null hypothesis. If the treatment actually has no effect, which of the following is true?

a) you have made a type I error b) you have made a type II error* c) you might have made a type I error, but the probability is only 5% at most d) you have made the correct decision

You complete a hypothesis test using a = .05, and based on the evidence from the sample, your decision is to reject the null hypothesis. If the treatment actually has no effect, which of the following is true?

a) you have made a type I error* b) you have made a type II error c) you might have made a type I error, but the probability is only 5% at most d) you have made the correct decision

Which of the following symbols identifies the population standard deviation? a) σ b) σ 2 c) N d) s

a) σ

For the population, would a score of X = 85 be considered a central score (near the middle of the distribution) or an extreme score (far out in the tail of the distribution)? Mean = 75, standard deviation = 15. a) All of these answers are true. b) Extreme Score c) Central Score d) Average Score

b) Extreme Score

Which of the following is a consequence of increasing variability? a) The distance from one score to another tends to increase, and a single score tends to provide a more accurate representation of the entire distribution. b) The distance from one score to another tends to increase, and a single score tends to provide a less accurate representation of the entire distribution. c) The distance from one score to another tends to decrease, and a single score tends to provide a more accurate representation of the entire distribution. d) The distance from one score to another tends to decrease, and a single score tends to provide a less accurate representation of the entire distribution.

b) The distance from one score to another tends to increase, and a single score tends to provide a less accurate representation of the entire distribution.

A z-score establishes a relationship between the score, mean, and _____________. Question options: a) standard deviation. b) the range. c) the variance. d) the degrees of freedom.

b) the range.

Which z-score value represents the location farthest from the mean? a) z = +0.50 b) z = -2.00 c) z = -0.50 d) z = -1.00

b) z = -2.00

A person's phone bills for the last three months were $20, $75, and $55, respectively. What was the mean average amount for the three phone bills? a) $65 b) $50 c) $55 d) $60

b) $50

Question 2 Which z-score corresponds to a score that is above the mean by 2 standard deviations? a) -2 b) +2 c) This is impossible to determine without knowing the value of the standard deviation. d) +10

b) +2

If the mean on an intelligence test is 100, what score indicates an excellent score? Question options: a) 45 b) 100 c) 55 d) 145

b) 100

What is the median for the following set of scores? Scores: 1, 5, 11, 12, 20 a) 8 b) 11 c) 11.5 d) 5

b) 11

What is the value of SS (sum of squared deviations) for the following population? Population: 1, 1, 1, 5. The mean is 2. a) 6 b) 12 c) 7 d) 2

b) 12

What is the mode for the following sample of n = 11 scores? Scores: 1, 2, 2, 2, 3, 3, 4, 5, 6, 6, 7 a) 3 b) 2 c) 6 d) 2.5

b) 2

The first quartile (Q1) = percentile rank of _______? a) 75 b) 25 c) 100 d) 50

b) 25

Which statement below must be false regarding a distribution of scores? a) 75% of the scores are the same value as the mode b) 75% of the scores are above the median c) 75% of the scores are above the mode d) 75% of the scores are above the mean

b) 75% of the scores are above the median

______________________is the spread of those scores based on the range of scores and the frequency of each. a) Frequency b) Distribution c) Skewed d) Variable

b) Distribution

What is the shape of this distribution? a) Symmetrical b) Negative skew c) Bimodal d) Positive skew

b) Negative skew

When would you use a grouped frequency table? a) When you only have 2 raw scores. b) When you have a wide range of data. c) When you only have 5 raw scores. d) When there isn't a wide range of data.

b) When you have a wide range of data.

If the variability is high, the majority of the scores are ___________. a) on the lower end of the distribution. b) spread out across the distribution. c) near the mean. d) on the higher end of the distribution.

b) spread out across the distribution

A large z indicates... Question options: a) a moderate score. b) a non-significant score. c) an extreme score. d) a small score.

c) an extreme score.

Which position in a distribution corresponds to a z-score of z = -1.00? a) below the mean by 1 point b) above the mean by 1 point c) below the mean by 1 standard deviation d) above the mean by 1 standard deviation

c) below the mean by 1 standard deviation

The numerical value of the z-score specifies the distance from the __________. Question options: a) X Score b) standard deviation c) mean d) variance

c) mean

A person scores X = 65 on an exam. Which set of parameters would give this person the worst grade on the exam relative to others? Question options: a) µ = 70 and σ = 10 b) Can't be determined. c) µ = 70 and σ = 5 d) µ = 60 and σ = 10

c) µ = 70 and σ = 5

If ƒ is 1 and n is 20, what is p (i.e., the proportion)? Use the proportion equation to solve this problem. a) 0.25 b) 0.35 c) 0.05 d) 0.10

c) 0.05

What is the sum or squares (SS) for the following scores? Scores 0, 6, 6, 8. N = 4. The mean is 5. a) 100 b) 25 c) 36 d) 400

c) 36

For the following data, N = _____. X | f 4 | 2 3 | 3 2 | 1 1 | 2 a) 18. b) 10. c) 8. d) 20.

c) 8

What is the range for the following set of scores? Scores 5, 8, 7, 9, 2, 10 a) 4 points b) 13 points c) 8 points d) 5 points

c) 8 points

The mean is the.. a) The middle score b) Most frequent score c) Average score d) The lowest score

c) Average score

Which statement below is correct regarding a grouped frequency distribution table? a) Interval widths should be restricted to either 10 or 20. b) The bottom score in each class interval should be divisible by 5. c) The ∑x cannot be determined. d) The ∑f cannot be determined.

c) The ∑x cannot be determined.

For a population with µ = 40 and σ = 8, what is the z-score corresponding to X = 34? Question options: a) z = -0.50 b) z = -1.50 c) z = -0.75 d) z = -1.00

c) z = -0.75

Z-scores are useful with regard to inferential statistics primarily because they offer a tool by which to determine whether _____. Question options: a) an individual is different from a sample. b) a distribution of scores is symmetrically shaped. c) a sample is noticeably different from a population. d) a distribution of scores is standardized.

d) a distribution of scores is standardized.

If ƒ is 2 and n is 20, what is p (i.e., the proportion)? Use the proportion equation to solve this problem. Question options: a) 0.15 b) 0.05 c) 0.20 d) 0.10

d) 0.10

Calculate the mean for the random sample of psychology students, 3, 2, 2, 2, 2, 1, 1, 1. n = 8 ΣX = 14 a) 2 b) 1.88 c) 1.60 d) 1.75

d) 1.75

A set of scores ranges from a high of X = 18 to a low of X = 5. If these scores were put in a grouped frequency distribution table with an interval width of 2 points, which of the following would be the top interval in the table? a) 17-18 b) 5-6 c) 4-5 d) 18-19

d) 18-19

What is the median for the numbers below? 2, 4, 6, 8, 10, 12, 14, 16 a) 10 b) 8 c) 6 d) 9

d) 9

What is the mean from the list of scores below: 5 5 5 a) M = 15 b) M = 10 c) M = 20 d) M = 5

d) M = 5

A distribution of scores is positively skewed. Which is the most probable order, from smallest to largest, for the three measures of central tendency? a) Median, mean, mode b) Mean, median, mode c) Mean, mode, median d) Mode, median, mean

d) Mode, median, mean

What kind of formula is this? z = X - μ σ a) Melissa Sollom's made up formula b) Sample c) E = MC^2 d) Population

d) Population

Which of the following actions will always change the value of the mean? Question options: a) removing a score from the distribution b) adding a new score to the distribution c) adding the same amount to each score in a distribution. d) changing the value of one score

d) changing the value of one score

If a distribution of scores is shown in a bar graph, the scores were measured using a(n) _____ scale of measurement. a) interval or ratio b) nominal or interval c) ordinal or interval d) nominal or ordinal

d) nominal or ordinal

What is the proportion equation? Question options: a) p = n/ƒ b) n = ƒ/n c) ƒ = p/n d) p = ƒ/n

d) p = ƒ/n

Which of the following phrases is not consistent with central tendency as a statistical measure? a) average score b) most typical score c) middle score d) spread of scores

d) spread of scores

T/F The range and the variance are both measures of distance.

true