PSYC 210 Pre- Quizzes

The correct formula for Cohen's d for a single-sample t test is:

(M- µ)/s.

The range of the correlation coefficient is always:

-1 to 1

A correlation value of _____ indicates that there is no association between the two variables.

0

According to Cohen's conventions, a d value of _____ indicates a medium effect.

0.5

According to Cohen's conventions, a d value of _____ indicates a large effect.

0.8

In an independent-samples t test, each group has N minus _____ degree(s) of freedom.

1

What is the mode of the following data set: 3, 17, 22, 5, 4, 16, 27, 22, 17, 22, 5, 3?

10.5---wrong

If there are at least _____ participants in a study, it is likely that the normality assumption is met.

30

In order to assess the effect of pet ownership on health, a researcher surveys 150 people who own pets and 150 people who do not own pets. The sample being studied is:

300 people

If dfbetween = 5, then there are _____ groups in the study.

6

Approximately _____ percent of scores fall within 2 standard deviations of the mean.

96

To make comparisons between three or more groups for differences on a dependent variable, use a(n) _____.

ANOVA

______ is a measure of effect size for an independent-samples t test.

Cohen's d

To calculate the effect size for an independent-samples t test, use:

Cohen's d.

Populations that have the same variance are referred to as homoscedastic.

True

The equation for the paired-samples t test is the same as that for the single-samples t test except that the data are now difference scores.

True

The distribution of means is more variable than the distribution of scores.

false

The percentage of area under the curve for a negative z score will be negative.

false

The population mean is the middle of a confidence interval.

false

Random _____ is what researchers do with participants once they have been recruited into a study.

assignment

If there are more than two levels of the independent variable and different participants were exposed to each level of the independent variable, then one should analyze the data with a(n) _____ ANOVA.

between-groups

A researcher compares 3 different types of dog owners on some dependent measure. The variability between the 3 groups of dog owners is known as _____.

between-groups variability

When a variable cannot take on values above a certain level, this is known as a(n) _____ effect.

ceiling

The _____ bias is the tendency to pay attention to evidence that supports one's beliefs and ignore that which does not.

confirmation

The ability to apply research findings to contexts or samples other than the one studied is called _____.

contextual-- worng

Variables for which an infinite number of potential values exist are:

continuous

The _____ group is the group that does not receive the intervention or treatment of interest.

control

A type of sample in which participants are selected because they are readily available is a _____ sample.

convenience

The _____ is the test statistic value beyond which one rejects the null hypothesis.

critical value

A paired-samples t test is also known as a:

dependent-samples t test.

The correlation of height and income is 0.25, and the correlation of depression and satisfaction with work is -0.42. Which is a stronger correlation and why?

depression and work satisfaction; -0.42 is closer to -1 than 0.25 is to 1.

Which "branch" of statistics uses numerical observations and incorporates them into an organized and informative summary of the data?

descriptive

What is the correct formula for calculating degrees of freedom for an independent-samples t test?

dftotal= (X1 + Y2) - 1--- wrong

Maria wants to know if identical twins raised in different environments have different IQ scores. What type of research design is NOT available for Maria to use because she cannot randomly assign the participants?

experimental

A nonparametric test is based on a set of assumptions about the population.

false

Effect size cannot be calculated for the independent-samples t test.

false

If two variables are negatively correlated, then low scores on one variable would be associated with low scores on the other variable.

false

If two variables are positively correlated, then high scores on one variable would be associated with low scores on the other variable.

false

Less than 5 percent of the distribution of scores falls beyond a z score of +/-1.0.

false

Random samples are used more often in research than convenience samples.

false

Raw scores are scores that have been modified from their original form.

false

The amount of overlap between two distributions can be decreased if their means are closer together.

false

The standard deviation of the population is commonly used to estimate the standard deviation of the sample.

false

The sum of squares is symbolized as Σx.

false

Two-tailed tests have more statistical power than one-tailed tests.

false

When computing the confidence interval for a t test, the cutoffs for the 95% interval are always the same.

false

When reporting the test results for an independent-samples t test, Nis reported rather than degrees of freedom.

false

The ttest is used when the standard deviation of the population is known.

false; the ttest is used when mean and standard deviation are not known

Correlation coefficients at or near -1.00 or 1.00 are relatively common.

fasle

Any raw score can be converted into a zscore, as long as you know the mean and median of the distribution.

flase

When a variable cannot take on values below a certain level, this is known as a(n) _____ effect.

floor

A(n) _____ shows the pattern of data by indicating how many participants had each possible score.

frequency table

A z score of -1.0 is _____ a z score of -2.0.

higher than

Seeing an association between two events that are unrelated is a(n) _____.

illusory correlation

As the overlap between distributions being compared decreases, the effect size:

increases

A variable that is manipulated to determine its effects on another variable is a(n) _____ variable.

independent

When the outcome of one trial does not depend, in any way, on the outcome of previous trials, the events are said to be _____.

independent

A group of rats that received a steroid drug supplement ran faster than a group of rats that did not receive the drug supplement. Which type of statistical test should be used to analyze these results?

independent-samples t test

In a(n) _____ t test, the samples of participants are from different groups, while in the a(n) _____ t test, participants are from the same group.

independent-samples; paired-samples

A larger effect size indicates that there is _____ overlap of two distributions.

less

The final step in hypothesis testing for an independent-samples t test is:

making a decision and communicating your results.

An independent-samples t test compares differences between sample _____.

means

The 50th percentile is always the _____.

median

A _____ is a study that involves the calculation of a mean effect size from the individual effect sizes of many studies.

meta-analysis

The most frequently occurring score in a distribution is the _____.

mode

A z score below the mean will always be _____.

negative

The older a male professor, the lesser the amount of hair on his head. As the age of a male professor increases, the hair on his head decreases. This is an example of what type of correlation?

negative

If two variables are _____ correlated, people who have high scores on one variable will tend to have low scores on the other variable.

negatively

Whenever data are based on a(n) _____ scale of measurement, the measure of central tendency that should be used is the mode.

nominal

The appropriate research hypothesis for a one-way ANOVA that is comparing 3 groups is

not all µs are equal

A statement that two populations are not different from one another is a(n) _____ hypothesis.

null

The "boring" hypothesis that says there is no difference between comparison groups is called the _____ hypothesis.

null

What is the term used to specify operations or procedures used to measure or manipulate a variable?

operational definition

There are three different types of Olympic medals: gold, silver, and bronze. Which scale of measurement describes the different types of medals?

ordinal

A _____ test makes a set of assumptions about the population, whereas a _____test does not.

parametric; nonparametric

A sample statistic using just one number to estimate a population parameter is a(n) _____.

point estimate

Numbers that describe a(n) _____ are called parameters.

population

As the age of a male professor increases, his income increases. The older a male professor, the higher his income. This is an example of_____ correlation

positive

If two variables are _____ correlated, people who have high scores on one variable will tend to have high scores on the other variable.

positively

Statistical _____ is the probability of successfully rejecting the null hypothesis.

power

A range of sample statistics used to estimate a population parameter is a(n) _____.

power calculation wrong

The _____ is a measure of variability that is calculated by taking the difference between the highest and lowest scores in the distribution.

range

A person's age, as measured in whole years, is an example of which scale of measurement?

ratio

A(n) _____ is a data point that has not yet been transformed or analyzed.

raw score

A(n) _____ variable gets consistent results, that is, it produces the same assessment over time for an unchanging variable.

reliable

The duplication of the results of a research study in a different context or with a different sample is called _____.

replication

The term _____ refers to the duplication of scientific results.

replication

A statement that two populations are different from one another is a(n) _____ hypothesis.

research

The "exciting" hypothesis that says there is a difference between comparison groups is called the _____ hypothesis.

research

A positively skewed distribution has a long tail to the _____ of the distribution, while a negative skew has a long tail to the _____ of the distribution.

right; left

Tests that are reliable even when statistical assumptions underlying the population are not met are referred to as _____.

robust

The confidence interval is centered around the mean of the _____.

sample

The direction of a correlation is indicated by its _____.

sign

The F distribution is

skewed right

According to Cohen's (1988) guidelines, an r of 0.29 would be considered a _____ correlation.

small- wrong

A common measure of spread for a distribution of scores is the standard deviation, and a common measure of spread for a distribution of means is the:

standard error.

Making meaningful comparisons of variables, even when they were measured on different scales, requires converting those variables to a common scale. This process is called:

standardization.

If the data differ from what one would expect if chance was the only thing operating, the finding is called _____.

statistically significant

The _____ of a correlation captures how closely related two sets of data points are.

strength

A z score is the distance a score is from the mean of its distribution, expressed in units of standard deviation.

true

In hypothesis testing, critical values are the:

test statistic or cut-off value beyond which we reject the null hypothesis.

The central limit theorem asserts that as sample size increases:

the distribution of means becomes more normal.

In order to conduct a single-sample t test, one needs to know:

the population mean and all properties of the sample.

A nondirectional test looks in both tails of the distribution.

true

A nondirectional test looks in neither tail of the distribution.

true

A score equal to the mean of its distribution falls at the 50th percentile.

true

An operational definition specifies the operations or procedures used to measure or manipulate a variable.

true

Effect size indicates the size of the difference between the sample and the null hypothesized value, unaffected by sample size.

true

For a one-tailed t test, there is only one critical cutoff value.

true

For an independent-samples t test, the test statistic is compared to a distribution of differences between means.

true

If two variables are positively correlated, then high scores on one variable would be associated with high scores on the other variable.

true

In a negatively skewed distribution, the tail extends to the left.

true

It is advisable to use a grouped frequency table when depicting the frequency of interval data that vary over a large range of numbers in table format.

true

Normal distributions are symmetric and inherently have no skew.

true

Statistical power calculations help researchers know how many participants are needed in their study.

true

The F ratio measures two sources of variability: within-groups variance and between-groups variance.

true

The confidence interval for an independent-samples t test is an interval estimate.

true

The independent-samples t test is considered a between-groups design.

true

The most common measure of variability reported in research articles is the standard deviation.

true

The null hypothesis can express that there is no relationship between variables or that no change is expected.

true

The standard deviation of a sample can be used to estimate the standard deviation of a population.

true

The strength of a correlation coefficient is independent of its sign.

true

To decide whether to reject the null hypothesis, we compare the test statistic to the critical value(s).

true

When creating a grouped frequency table, most researchers recommend using between 5 and 10 intervals.

true

In an independent-samples t test, each participant is assigned to _____ group(s).

two--- wrong

A false-positive is also known as a _____ error.

type 1

Standard deviation is computed by taking the square root of the _____.

variance

What measure of variability is the square root of the average of the squared deviations from the mean?

variance----wrong

A type of sample in which participants actively elect to participate is a(n) _____, or self-selected, sample.

volunteer

The major difference between the paired-samples t test and the single-samples ttest is that in the paired-samples t test:

we must create difference scores for every individual.

If there are more than two levels of the independent variable and the same participants were exposed to every level of the independent variable, then one should analyze the data with a(n) _____ ANOVA.

within-groups

A researcher compares 3 different types of dog owners on some dependent measure. The variability among all the dog owners, regardless of group, is known as _____.

within-groups variability

To compute a confidence interval when the population mean and standard deviation are known, you should use a(n) _____ distribution.

z