PSYCH 4400

Use the frequency distribution table to determine how many subjects were in the study. 10 15 33 Impossible to determine X f 5 2 4 4 3 1 2 0 1 3

10

A grouped frequency distribution table has categories 0-9, 10-19, 20-29, and 30-39. What is the width of the interval 20-29? 9 points 9.5 points 10 points 10.5 points

10 points (29.5 - 19.5 = 10)

A score of X = 59 comes from a distribution with μ = 63 and σ = 8. This distribution is standardized to a new distribution with μ = 50 and σ = 10. What is the new value of the original score? 59 45 46 55

45

For the scores shown in the stem and leaf display, what is the lowest score in the distribution? 7 15 50 51 9 374 8 945 7 7042 6 68 5 14

51

For a population with μ = 50 and σ = 10, what is the X value corresponding to z = 0.4? 50.4 10 54 10.4

54

A population has μ = 60 with σ = 5; the distribution of sample means for samples of size n = 4 selected from this population would have an expected value of _____. 5 60 30 15

60

Chapter SEVEN

BRUH

Decide if each of the following statements is True or False. T/F Any frequency distribution is suitable for a stem and leaf display. T/F A score of 54 is displayed as 5 (stem) and 4 (leaf) in a stem and leaf display.

False A stem and leaf display is a simple alternative for a grouped frequency distribution True The first digit (5) is the stem and the last digit (4) is the leaf

Decide if each of the following statements is True or False. T/F A sample mean with z = 3.00 is a fairly typical, representative sample. T/F The mean of the sample is always equal to the population mean.

False A z-score of 3.00 is an extreme, or unlikely, z-score False Individual samples will vary from the population mean

Decide if each of the following statements is True or False. T/F When the z-score is quite extreme, it shows that the null hypothesis is true. T/F A decision to retain the null hypothesis means that you proved that the treatment has no effect.

False An extreme z-score is in the critical region—this is very unlikely if H0 is true False Failing to reject H0 does not prove it true; there is just not enough evidence to reject the hypothesis

For which of the following would a repeated-measures study be appropriate? Testing a group of twins for IQ Comparing boys' and girls' strength at age 3 Evaluating the difference in self-esteem between athletes and nonathletes Testing students' knowledge in September and December

Testing students' knowledge in September and December

A sports coach is investigating the impact of a new training method. In words, what would the null hypothesis say? The new training program produces different results from the existing one. The new training program produces results similar to the existing one. The new training program produces better results than the existing one. There is no way to predict the results of thenew training program.

The new training program produces results similar to the existing one.

The results of a hypothesis test are reported as follows: t(21) = 2.38, p < .05. What was the statistical decision and how big was the sample? The null hypothesis was rejected using a sample of n = 21. The null hypothesis was rejected using a sample of n = 22. The null hypothesis was not rejected using a sample of n = 21. The null hypothesis was not rejected using a sample of n = 22.

The null hypothesis was rejected using a sample of n = 22.

A sample of four scores has SS = 24. What is the variance? The variance is 6. The variance is 7. The variance is 8. The variance is 12.

The variance is 8

Decide if each of the following statements is True or False. T/F An effect that exists is more likely to be detected if n is large. T/F An effect that exists is less likely to be detected if σ is large.

True A larger sample produces a smaller standard error and larger z True A larger standard deviation increases the standard error and produces a smaller z

Decide if each of the following statements is True or False. T/F If the alpha level is decreased, the size of the critical region decreases. T/F The critical region defines unlikely values if the null hypothesis is true.

True Alpha is the proportion of the area in the critical region(s) True This is the definition of unlikely

Decide if each of the following statements is True or False. T/F Cohen's d is used because alone, a hypothesis test does not measure the size of the treatment effect. T/F Lowering the alpha level from .05 to .01 will increase the power of a statistical test.

True Differences might be significant but not of substantial size False It is less likely that H0 will be rejected with a small alpha

Decide if each of the following statements is True or False. T/F A repeated-measures study requires 20 participants to obtain 20 scores in each of the conditions being compared. T/F As the variance of the difference scores increases, the magnitude of the t statistic decreases.

True Each subject is tested in all treatment conditions, so only 20 subjects are required True Increasing the variance increases the denominator and decreases the t statistic

Decide if each of the following statements is True or False. T/F A sample systematically has less variability than a population. T/F The standard deviation is the distance from the mean to the farthest point on the distribution curve.

True Extreme scores affect variability, but are less likely to be included in a sample False The standard deviation extends from the mean approximately halfway to the most extreme score

Chapter THREE

YAS

CHAPTER ONE

YAY

Chapter TWO

YAY

Which combination of factors is most likely to produce a significant value for an independent-measures t statistic? a small mean difference and small sample variances a large mean difference and large sample variances a small mean difference and large sample variances a large mean difference and small sample variances

a large mean difference and small sample variances

A researcher is interested in the effect of amount of sleep on high school students' exam scores. A group of 75 high school boys agree to participate in the study. The boys are _____. A statistic A variable A parameter A sample

a sample

A distribution of scores shows the mean = 31 and the median = 43. This distribution is probably _____. positively skewed negatively skewed bimodal open-ended

negatively skewed

Membership of MENSA requires a score of 130 on the Stanford-Binet 5 IQ test, which has μ = 100 and σ = 15. What proportion of the population qualifies for MENSA? p = 0.0228 p = 0.9772 p = 0.4772 p = 0.0456

p = 0.0228

Find the proportion of the normal curve that corresponds to z > 1.50. p = 0.9332 p = 0.5000 p = 0.4332 p = 0.0668

p = 0.0668

A deck of 52 cards contains 12 royalty cards. If you randomly select a card from the deck, what is the probability of obtaining a royalty card? p = 1/52 p = 12/52 p = 3/52 p = 4/52

p = 12/52

What is the shape of this distribution? symmetrical negatively skewed positively skewed discrete

positively skewed

The power of a statistical test is the probability of _____ null hypothesis. rejecting a true supporting a true rejecting a false supporting a false null hypothesis

rejecting a false

∑X2 + 47 instructs you to _____. A. Square each score and add 47 to it, then sum those numbers B. Square each score add up the squared scores, then add 47 to that sum C. Add 47 to each score, square the result, and sum those numbers D. Add up the scores, square that sum, and add 47 to it

square each score add up the squared scores, then add 47 to that sum

The standard deviation measures the _____. sum of squared deviation scores standard distance of a score from the mean average deviation of a score from the mean average squared distance of a score from the mean

standard distance of a score from the mean

Decide if each of the following statements is True or False. T/F A biased statistic has been influenced by researcher error. T/F On average, an unbiased sample statistic has the same value as the population parameter.

False Bias refers to the systematic effect of using sample data to estimate a population parameter True Each sample's statistic differs from the population parameter, but the average of all samples will equal the parameter

Decide if each of the following statements is True or False. T/F Variables that cannot be measured directly cannot be studied scientifically T/F Research measurements are made using specific procedures that define constructs

False Constructs (interval states) can only be observed indirectly, but can be operationally measured True Operational definitions assure consistent measurement and provide construct definitions

Decide if each of the following statements is True or False. T/F All research methods have an independent variable T/F All research methods can show cause-and-effect relationships

False Correlational methods do not need an independent variable False Only experiments control the influence of participants and environmental variables

Decide if each of the following statements is True or False. T/F For any negative z-score, the tail will be on the right-hand side. T/F If you know the probability, you can find the corresponding z-score.

False For negative z-scores the tail will always be on the left side True First find the proportion in the appropriate column, then read the z-score from the left column

Decide if each of the following statements is True or False. T/F If μ = 40 and 50 corresponds to z = +2.00, then σ = 10 points. T/F If σ = 20, a score above the mean by 10 points will have z = 1.00.

False If z = +2, then 2σ = 10, so σ = 5 False If σ = 20, then z = 10/20 = 0.5

Decide if each of the following statements is True or False. T/F It would be correct to use a histogram to graph parental marital status data (single, married, divorced...) from a treatment center for children. T/F It would be correct to use a histogram to graph the time children spent playing with other children from data collected in a children's treatment center.

False Marital status is a nominal variable; a bar graph is required True Time is measured continuously and is an interval variable

Decide if each of the following statements is True or False. T/F Sample size has a great influence on measures of effect size. T/F When the value of the t statistic is near 0, the null hypothesis should be rejected.

False Measures of effect size are not influenced to any great extent by sample size False When the value of t is near 0, the difference between M and μ is also near 0

Decide if each of the following statements is True or False. T/F Choosing random individuals who walk by you yields a random sample. T/F Probability predicts what kind of population is likely to be obtained.

False Not all individuals walk by, so not all have an equal chance of being selected for the sample False The population is given; probability predicts what a sample is likely to be like

Decide if each of the following statements is True or False. T/F Increasing the sample size will also increase the effect size, T/F Larger differences between the sample and population mean increase effect size.

False Sample size does not affect Cohen's d True The mean difference is in the numerator of Cohen's d

Decide if each of the following statements is True or False. T/F The homogeneity assumption requires the two sample variances to be equal T/F If a researcher reports that t(6) = 1.98, p > .05, then H0 was rejected

False The assumption requires equal population variances but the test is valid if sample variances are similar False H0 is rejected when p < .05, and t > the critical value of t

Decide if each of the following statements is True or False. T/F The computational and definitional formulas for SS sometimes give different results. T/F If all the scores in a data set are the same, the standard deviation is equal to 1.00.

False The computational formula is just an algebraic rearrangement of the definitional formula. Results are identical. False When all the scores are the same, they are all equal to the mean. Their deviations = 0, as is their standard deviation.

Decide if each of the following statements is True or False. T/F The mean uses all of the scores in the data, so it is the best measure of central tendency for skewed data. T/F If the mean and median have the same values, the distribution is probably symmetrical.

False The mean will be moved toward the long tail in skewed data so may not be at all representative of the "middle" True When mean and median are the same, the distribution has to be symmetrical (balanced about M; 50% above/below)

Decide if each of the following statements is True or False. T/F The shape of a distribution of sample means is always normal. T/F As sample size increases, the value of the standard error decreases.

False The shape is normal only if the population is normal or n ≥ 30 True Sample size is in the denominator of the equation so as n grows larger, standard error decreases

Decide if each of the following statements is True or False. T/F By chance, two samples selected from the same population have the same size (n = 36) and the same mean (M = 83). That means they will also have the same t statistic. T/F Compared to a z-score, a hypothesis test with a t statistic requires less information about the population.

False The two t values are unlikely to be the same; variance estimates (s2) differ between samples True The t statistic does not require the population standard deviation; the z-test does

Decide if each of the following equationsis True or False T/F ∑X2 = (∑X)2 T/F (∑X) • (∑X) = (∑X)2

False When the operations are performed in a different order, the results will be different True This is the definition of (∑X)2

Decide if each of the following statements is True or False. T/F If both samples have n = 10, the independent-measures t statistic will have df = 19. T/F For an independent-measures t statistic, the estimated standard error measures how much difference is reasonable to expect between the sample means if there is no treatment effect.

False df = (n1 - 1) + (n2 - 1) = 9 + 9 = 18 True This is an accurate interpretation

Chapter EIGHT-ELEVEN

LETS GET IT

A sample of n = 7 scores has M = 5. All of the scores are doubled. What is the new mean? M = 5 M = 10 M = 25 More information is needed to compute M.

M=10

Decide if each of the following statements is True or False. T/F It is possible to find the X score corresponding to a percentile rank in a normal distribution. T/F If you know a z-score, you can find the probability of obtaining that z-score in a distribution of any shape.

True Find the z-score for the percentile rank, then transform it to X False If a distribution is skewed, the probability shown in the unit normal table will not be accurate

Decide if each of the following statements is True or False. T/F A Type I error is like convicting an innocent person in a jury trial. T/F A Type II error is like convicting a guilty person in a jury trial.

True Innocence is the "null hypothesis" for a jury trial; conviction is like rejecting that hypothesis False Convicting a guilty person is not an error; but acquitting a guilty person would be like a Type II error

Decide if each of the following statements is True or False. T/F It is possible for more than 50% of the scores in a distribution to have values above the mean. T/F It is possible for more than 50% of the scores in a distribution to have values above the median.

True More than 50% of the scores in a negatively skewed distribution will be above the mean False The median is defined as the score that divides the distribution exactly in half—50% above/below

Decide if each of the following statements is True or False. T/F Most research studies data from samples T/F When sample differs from the population there is a systematic difference between groups

True Samples used because it is not feasible or possible to measure all individuals in the population False Sampling error due to random influence may produce unsystematic group difference

For the frequency distribution shown, is each of these statements True or False? T/F More than 50% of the individuals scored above 3. T/F The proportion of scores in the lowest category was p = 3. X f 5 2 4 4 3 1 2 0 1 3

True Six out of ten individuals scored above 3 = 60% = more than half False A proportion is a fractional part; 3 out of 10 scores = 3/10 = .3

Decide if each of the following statements is True or False. T/F Transforming an entire distribution of scores into z-scores will not change the shape of the distribution. T/F If a sample of n = 10 scores is transformed into z-scores, there will be five positive z-scores and five negative z-scores.

True The location of each score relative to all other scores is unchanged, so the shape of the distribution is unchanged False The number of z-scores above/below the mean will be exactly the same as the number of original scores above/below the mean

Decide if each of the following statements is True or False. T/F You can determine how many individuals had each score from a frequency distribution table. T/F You can determine how many individuals had each score from a grouped frequency distribution.

True The original scores can be recreated from the frequency distribution table False Only the number of individuals in the class interval is available once the scores are grouped

Decide if each of the following statements is True or False. T/F A negative z-score always indicates a location below the mean T/F A score close to the mean has a z-score close to 1.00

True The sign indicates that score is below the mean False Scores quite close to the mean have z-scores close to 0.00

Decide if each of the following statements is True or False. T/F Compared to independent-measures designs, repeated-measures designs reduce the variance by removing individual differences. T/F The repeated-measures t statistic can be used with either a repeated-measures or a matched-subjects design.

True Using the same subjects in both treatments removes individual differences across treatments True Both of these related-samples tests reduce individual differences across treatments

A z-score of z = +1.00 indicates a position in a distribution _____. above the mean by 1 point above the mean by a distance equal to 1 standard deviation below the mean by 1 point below the mean by a distance equal to 1 standard deviation

above the mean by a distance equal to 1 standard deviation

Last week Andy had exams in chemistry and in Spanish. On the chemistry exam, the mean was µ = 30 with σ = 5, and Andy had a score of X = 45. On the Spanish exam, the mean was µ = 60 with σ = 6, and Andy had a score of X = 65. For which class should Andy expect the better grade? chemistry Spanish There is not enough information to know.

chemistry

Researchers observed that students' exam scores were higher the more sleep they had the night before. This study is _____. A. Descriptive B. Experimental comparison of groups C. Non-experimental group comparison D. Correlational

correlational

Assuming that the sample mean difference remains the same, which of the following sets of data is most likely to produce a significant t statistic? n = 15 and SS = 10 n = 15 and SS = 100 n = 30 and SS = 10 n = 30 and SS = 100

n = 30 and SS = 10

A study assesses the optimal size (number of other members) for study groups. The variable size of group is _____. Discrete and interval Continuous and ordinal Discrete and ratio Continuous and interval

discrete and ratio

Chapter FOUR

hehehehe

Chapter FIVE

hehhe

For an independent-measures research study, the value of Cohen's d or r2 helps to describe _____. the risk of a Type I error the risk of a Type II error how much difference there is between the two treatments whether the difference between the two treatments is likely to have occurred by chance

how much difference there is between the two treatments

When n is small (less than 30), the t distribution _____. is almost identical in shape to the normal z distribution is flatter and more spread out than the normal z distribution is taller and narrower than the normal z distribution cannot be specified, making hypothesis tests impossible

is flatter and more spread out than the normal z distribution

A researcher is predicting that a treatment will decrease scores. If this treatment is evaluated using a directional hypothesis test, then the critical region for the test _____. would be entirely in the right-hand tail of the distribution would be entirely in the left-hand tail of the distribution would be divided equally between the two tails of the distribution cannot be identified without knowing the value of the alpha level

would be entirely in the left-hand tail of the distribution

Chapter SIXXXX

yuh

A random sample of n = 16 scores is obtained from a population with µ = 50 and σ = 16. If the sample mean is M = 58, the z-score corresponding to the sample mean is _____? z = 1.00 z = 2.00 z = 4.00 cannot determine

z = 2.00

A sample of n = 12 scores has a mean of M = 8. What is the value of ΣX for this sample? ΣX = 1.5 ΣX = 4 ΣX = 20 ΣX = 96

ΣX = 96

A population has μ = 6 and σ = 2. Each score is multiplied by 10. What is the shape of the resulting distribution? μ = 60 and σ = 2 μ = 6 and σ = 20 μ = 60 and σ = 20 μ = 6 and σ = 5

μ = 60 and σ = 20

A researcher uses a hypothesis test to evaluate H0: µ = 80. Which combination of factors is most likely to result in rejecting the null hypothesis? σ = 5 and n = 25 σ = 5 and n = 50 σ = 10 and n = 25 σ = 10 and n = 50

σ = 5 and n = 50