Stats Final Review

there separate F-ratios

A 2-factor ANOVA for independent groups produces __________.

The z-score distribution will be negatively skewed.

A distribution of exam scores is negatively skewed with M = 85 and s = 12. If these students' scores are transformed into z-scores, what will be the shape of the z-scores distribution?

Negatively skewed

A population of scores has a mean of µ = 16, a median of 22, and a mode of 19. What is the most likely shape of this population distribution?

A significant interaction between teaching strategy and student motivation.

A researcher conduct a 2-factor ANOVA on results of a study that compares a new teaching strategy relative to the old strategy. It is predicted that the new teaching strategy will increase test scores for highly motivated students but will decrease scores for student with low motivation. This researcher is predicting __________.

The amount of St. Johns Wort given to each participant, daily dose or placebo.

A researcher conducts and experiment to determine whether a daily doses of St. Johns Wort (i.e., herbal supplement) will reduce anxiety among college students. Each day, one group of participants was given a dose of St. Johns Wort, and a second group was given a placebo pill. After 6-weeks, the researcher used Anxiety Questionnaire to assess anxiety level of all participants. What is the independent variable in this study?

No significant interaction between special training and gender

A researcher examines the effect of gender and special training on task performance using a 2-factor ANOVA for independent samples. He predicts that a special training course will be equally effective for males and females. That means the researcher is expecting to find __________.

Correlation Study

A researcher interested in a relationship between amount of sleep and stress recorded a typical number of sleep hours per night and current stress level of each participant of the study. This study is an example of __________.

Negative correlation

A researcher measures weekly average time spent on physical exercise and body weight in a sample of college students. What kind of correlations is likely to be obtained for theses two variables?

The researcher made a mistake, the value of Chi^2 cannot be negative.

A researcher obtains a negative value for Chi^2 statistic. What can you conclude because the value is negative?

µ = 40

A researcher selects a sample from a population with a mean of µ = 40 and administers a treatment to the individuals in the sample. The following is the correct statement of the null hypothesis for a two-tailed t-test for a single sample.

Sample

A researcher uses an on-line survey to investigate the social media use habits of American adolescents. Base on the 1500 surveys that were completed and returned by teenagers enrolled to the study, the researcher finds that they spend and average of 2.5 hours each day on social networking. For this study, the set of 1500 teens who returned surveys is an example of a __________.

Population

A researcher uses an on-line survey to investigate the social media use habits of American adolescents. Based on the 1500 surveys that were completed and returned by teenagers enrolled to the study, the researcher finds that they spend an average of 2.5 hours each day on social networking. For this study, all American adolescents is an example of a __________.

Statistic

A researcher uses an on-line survey to investigate the social media use habits of American adolescents. Based on the 1500 surveys that were completed and returned by teenagers enrolled to the study, the researcher finds that they spend an average of 2.5 hours each day on social networking. For this study, the average 2.5 hours spent on social networking based on answers to 1500 surveys is an example of __________.

An experiment

A researcher would like to know if stress has a negative effect on memory performance. One group of participants was exposed to stress inducing noise and the second group listened to calming music. Afterwards, both groups were given memory test. The researcher compared the memory test scores of two groups. This study is an example of __________.

Quasi-experiment

A team of mental health researchers compared average social anxiety scores of female and male students on national college mental health survey, in order to determine if there is a gender differences in level of social anxiety. This study is an example of __________.

A significant main effect for Factor A - medication, and a significant interaction between Factor A (medication) and Factor B (gender)

A two-factor research study is used to evaluate the effectiveness of a new blood-pressure medication. In this two-factor study, Factor A - medication, has 2 levels (i.e., receiving medication versus no medication condition) and Factor B - Gender, has also two levels (i.e., male vs. females) Overall, the medication is expected to reduce blood pressure for both males and females, but it is expected to have a much greater effect for males. What pattern of results should be obtained in this study if the medication works as predicted?

Statistic

A value obtained from a sample and used to describe the sample.

Parameter

A value that is obtained from a population of scores and is used to describe the population.

A bar graph

After recording a final letter grade (i.e., A, B, C, D, F) for each student in a class of n-120 students, a professor would like to display the grade distribution in a frequency distribution graph. What kind of graph should he/she use?

The critical r gets smaller

As the sample size gets larger, what happens to the size of the critical value of Pearson's correlation that is needed to reject H0?

Check the scatter plot for the possibility of the curvilinear relationship between the variable, check the scatter plot for the possibility of restricted range problem, and check the scatter plot for the possibility of the outliers problem.

Before calculating a Pearson's correlation coefficient it is advisable to plot the data n order to __________.

At least one of the five population means is different form another mean.

For a one-factor ANOVA comparing five treatment conditions, what is stated by the alternative hypothesis (H1)?

There are no differences between any of the population means.

For a one-factor ANOVA comparing four treatment conditions, what is stated by the null hypothesis (H0)?

30

For a perfectly symmetrical distribution with a median of 30, what is the value of the mean?

There is a significant correlation in the population

For a two-tailed hypothesis test evaluating a significance of Pearson correlation, what is stated by the alternative hypothesis?

Positive correlation

For each participant of the study, a researcher records a number of study hours and number of correct answers on a test. What kind of correlation is likely to be obtained for these two variables?

The larger the difference, the larger the value of Chi^2 and the greater the likelihood of rejecting the null hypothesis.

How does the difference between frequencies expected (fe) and frequencies observed (fo) influence the outcome of a Chi^2 test?

Reject the null hypothesis

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

Longer sleep per night is associated with better memory capacity.

If a researcher found a significant positive Pearson's correlation between average number of sleep hours and memory capacity she/he can conclude that __________.

The researcher rejected H0 and found significant effect of stress on memory.

If a researcher report from an experiment investigating the effect of stress on memory states "t(40) = 2.31, p < .05." then __________.

Most of the students had relatively low scores.

If a set of exam scores form a positively skewed frequency distribution, what can you conclude about the students' scores?

It will decrease the estimated standard error and increase the likelihood of rejecting H0.

If other factors are held constant, what is the effect of increasing the sample size?

It will increase the estimated standard error and decrease the likelihood of rejecting H0.

If other factors are held constant, what is the effect of increasing the sample variance.

The lines are not parallel

If the results of a two-factor ANOVA are presented in a line graph, then an interaction between the two factors can be seen whenever __________.

MSwithin

In a one-factor ANOVA for independent samples, the following is directly affected by the size of the sample variance

between-treatment variance but not within-treatment variances

In a one-factor ANOVA, the mean differences between-groups caused by a treatment effect contribute to the following variances.

Oder effect

In a repeated-measure experiment, each individual participates in one treatment condition and then moves on to a second treatment condition. One of the major concerns in this type of study is that participation in the first treatment may influence the participant's score in the second treatment. What is this problem called?

The mean difference among different levels of one factor

In a two-factor analysis of variance, a main effect is defined as __________.

The average differences between sample means.

In one-factor ANOVA, what is measured by the MSbetweeen?

Around 1.00

On average, what is expected for the F-ratio if the null hypothesis, H0 is true?

Much greater than 1.00

On average, what value is expected for the F-ratio if the null hypothesis, H0 is true?

0

On average, what value is expected for the t statistic when the null hypothesis is true?

There is no difference between populations represent by two samples (i.e., µ1- µ2 = 0 or µ1 = µ2).

The following is the correct null hypothesis for an independent sample t-test (assume 2-tails test)

Around 70% of the scores will be located within one standard deviation of the mean (i.e., plus/minus one standard deviation of the mean).

The following is true for most frequencies.

Nominal

Students in the introduction to statistics class are classified as Seniors and non-Seniors. What scale of measurement is being used to classify the students?

The sing of a z-score

Tells whether the score is located above (+) or below (-) the mean, and the numerical value identifies the distance from the mean by measuring the number of standard deviations between the score and the mean.

frequency counts in nominal categories

The data for Chi^2 test consist of __________.

Sampling Error

The error or discrepancy between a statistic and the corresponding parameter

is computed based on the variance, s^2 of both samples

The estimated standard error, s(M1-M2) in the t-test for independent samples __________.

An inferential statistical method that uses the data from a sample to draw inferences about a population.

The following accurately describes a hypothesis test statistical method

Positively skewed with all values greater than or equal to zero.

The following accurately describes a shape of F distribution.

Sample means with a very low probability if the null hypothesis is true.

The following accurately describes outcomes in the critical region of the distribution of sample means for a z-test

Positively skewed with all values grater than or equal to zero

The following accurately describes the Chi^2 distribution?

Proportions in the right-hand tail are positive, and proportions in the left-hand tail are negative.

The following accurately describes the proportions of scores in the tails of a normal distribution

Subtract 5 points from every score in the distribution

The following action will have no effect on the value of the standard deviation.

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.

The following is a consequence of increasing variability in dataset.

The t statistic uses the sample variance in place of the population variance.

The following is a fundamental difference between the t statistic and a z-score

Every individual has an equal chance of being selected, the probabilities cannot change during a series of selections, and there must be a sampling with replacement.

The following is a requirement for random sampling

The amount of time to solve a problem.

The following is an example of continuous variable

The gender of each student in a psychology class.

The following is an example of discrete variable

Examining gender differences in analytical problem solving skills among undergraduate students.

The following research situation would be most likely to use a between-subject research design.

Comparing patients' pain tolerance at the beginning and at the end of physical therapy sessions

The following situation would be a repeated-measure research design be appropriate

When vey few subjects are available and individual difference are large.

The following situations would a repeated-measure design have the maximum advantage over an independent-measure design

60% of the scores are above the median.

The following statements cannot be true for a frequency distribution of scores.

σ

The following symbol identifies the population standard deviation

σ^2

The following symbol identifies the population variance

s

The following symbol identifies the sample standard deviation

s^2

The following symbol identifies the sample variance

The probability of supporting a false null hypothesis

The power of a statistical test

You cannot make any conclusion about the significance of the interaction (i.e., all three effects are independent from each other).

The results from a two-factor analysis of variance show a significant main effect for factor A and a significant main effect for factor B. Based on this information, what can you conclude about the interaction?

Distribution of Sample Means

The set of sample means obtained from all possible random samples of a specific size (n) selected from a particular population.

Standard error of M

The standard deviation for the distribution of sample means; it measure the standard (i.e., average) difference between a sample mean M and the population mean µ.

The population after treatment.

The statement of the null hypothesis refers to __________.

the mean difference between two treatment conditions in an experiment (e.g. a difference in performance of experimental group and control group), and the mean difference between two populations in quasi-experimental design (e.g. mean difference in attitudes to abortion between residents of the southern vs. northern states in the U.S.)

The t-test for independent sample can be used to examine __________.

z = -2.00

This z-score corresponds to a score that is below the mean by 2 standard deviations.

The effect of one independent variable depends on the levels of the second independent variable.

Two independent variables (i.e., factors) are said to interact when __________.

Rejecting a true null hypothesis

Type I error

Failing to reject a false null hypothesis

Type II error

When variables consists or ranks (i.e., are measure on ordinal scale), and when there is a non-linear relationship between variables.

Under what circumstances is the Spearman correlation used?

In an extremely skewed frequency distribution.

Under what circumstances is the median likely to produce a better measure of central tendency than the mean?

If fe < 5 for any cell

Under what circumstances should the Chi^2 test not be used.

If the population is normal or if the sample size is greater than 30

Under what circumstances will the distribution of sample means be normal

Wen either of the two variables consists of more than two categories.

Under what condition is Cramer's V used to measure effect size for Chi^2 test for independence?

The probability of a Type I error is determined by selecting the alpha level for the test. The choice of an alpha level does not affect the value of standard error.

What can a researcher do to influence the probability of a Type I error? Does this action have any effect on the size of standard error?

A standard error can be decreased by increasing the sample size. Changes in sample size have no effect on the probability of a Type I error

What can a researcher do to influence the size of the standard error? Does this action have any effect on the probability of a Type I error?

The critical value depends on the number of categories, not the sample size.

What happens to the critical value of Chi^2 test if the size of the sample increased?

The distribution of proportions (or percentages) across different categories in a population.

What is evaluated by the Chi^2 test for Goodness of Fit?

Each time X increase, there is a perfectly predictable increase in Y.

What is indicated by a Pearson correlation of r = 1.00 between X and Y?

The sample data (observed values) do not match the null hypothesis.

What is indicated by a large value for the Chi^2 statistic?

An inconsistent treatment effect and a low likelihood of a significant difference.

What is indicated by a large variance of a sample of difference scores (i.e, a large variance of D scores)?

Increase in X tend to be accompanied by decrease in Y

What is indicated by a negative value of Pearson's correlation?

The average distance between a sample mean M and the population mean µ that would be expected if H0 was true.

What is measured by the denominator of the z-score test statistic?

The actual distance between a sample mean M and a population mean µ.

What is measured by the numerator of the z-score test statistic?

The frequencies found in the sample data.

What is referred to by the term observed frequencies.

The frequencies that hypothesized for the population being examined (i.e., the frequencies computed from the null hypothesis).

What is referred to the by the term expected frequencies?

There is no relationship between two variables.

What is stated by the null hypothesis for the Chi^2 test for independence?

t =0

What is the average value expected for the independent-measures t statistic if the null hypothesis is true (i.e., the two samples represent the same population)?

To determine exactly which treatment groups significantly differ from other groups

What is the purpose of the post-hoc test such as Scheffe's test or Tukey's test?

As the alpha level increases, the size of the critical region increases, and the risk of a Type I error increases.

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

Below the mean by a distance equal to 1 standard deviation.

What position in the distribution corresponds to a z-score of z= -.01?

Ratio

What scale of measurement is used by a researcher who records a body weight for each participant

The value of an unknown population mean

What value is estimated with a confidence interval using the t statistic?

It is flatter and more spread out than the normal distribution.

When n is small (less than 30), how does the shape of the t distribution compare to the normal distribution?

A larger sample increases chi-square but has no effect on phi.

When the date of a 2X2 matrix, the phi-coefficient is used to measure effect size for the Chi^2 test for independence. If other factors are held constant, how does sample size influence the value for phi and Chi^2 statistic?

It is similar to a correlation because it evaluates the relationship between two variables.

Which of the following accurately describes the Chi^2 test for independence?

The observations must be independent

Which of the following is a basic assumption for a Chi^2 hypothesis test?