exam 4 stats hmm

When a researcher rejects the null hypothesis and the null hypothesis is actually true, what kind of error is this?

1

For an independent-samples t test, if N = 42, then the degrees of freedom will be:

40

Imagine you managed to measure every case in the population that you were interested in. Which statements below would be true? (Choose all that apply.)

All confidence intervals would contain only the true mean and no other values The standard error would be zero.

For matched samples, we're interested in the mean of differences, which is symbolically represented as

Dline

The _____ distribution is utilized in an analysis of variance (ANOVA) test for the multiple comparisons of population means.

F

How would you write the null hypothesis for an independent samples t test using symbolic notation? Choose all that apply.

H 0:μ 1 − μ 2 = 0 H 0:μ 1 = μ 2

Which assumption for the Independent-Samples t Test depends on the degree of variability in the two populations being equivalent?

Homogeneity of Variance

With one-way ANOVAs, the null hypothesis is represented by:

The Grand Mean

What is the standard error of the mean?

The standard deviation of the sampling distribution of the mean

ANOVA is always a two-tailed test.

True

Dr. Reed conducted a study to see whether listening to Wu Tang Clan albums improves vocabulary. He compared Wu Tang listeners to the rest of the population, using vocabulary measures that had a known population mean and standard deviation. Based on his results, Dr. Reed failed to reject the null hypothesis, which was unfortunate because in this case the null hypothesis should have been rejected. What type of error did Dr. Reed make?

Type II error

For t distributions, when the sample size gets large, the rare zone gets _________ and it is ________ to reject the null hypothesis.

closer to zero; easier

A range of values thought to contain the true mean of a population is called a

confidence interval

As the sample size_____ , the t distribution becomes flatter, with fewer cases in the middle and more cases in the tails

decreases

With paired-samples t-tests, the sampling distribution consists of:

difference scores

If a researcher is doing a one-tailed test, he/she should predict the ________ of the results before collecting any data.

direction

The change in our outcome variable that is due to our experimental manipulation is called the _____ .

effect

If we use a non-directional hypothesis, we are open to extreme differences found in ______ tail of the distribution.

either

The ability of a test to reject a _____ null hypothesis is known as ______

false; power

When is a post-hoc test used?

if the F ratio is greater than the critical value for F if the ANOVA is statistically significant

All other factors being equal, as an effect grows larger, the probability of rejecting a null hypothesis _____ .

increases

Assuming sample size stays the same, as the width of a confidence interval increases (including more values in the interval), our confidence that the interval contains the true population value _____ .

increases

With // samples, case selection for one sample does not influence how cases are selected for the other sample. This differs from // samples, in which the cases selected for one sample depend on the cases in the other sample.

independent/ paired

Effect sizes are used to quantify the impact of the variable on the variable.

independent; dependent

In a(n) _____ samples t test, the test focuses on the difference between the mean of one sample and the mean of the other sample.

indp

If the t-statistic observed is _______, then it is unlikely that the value we observed could occur from two random samples; it is likely to be due to the experimental manipulation.

large

The relationship between confidence level and interval width is such that as our confidence increases (from 95% to 99%, for example), the estimate will be come _____ precise.

less

As sample size increases, the confidence interval becomes _____ and _____ precise.

narrower; more

Assuming our sample size does not include the entire population, can we be absolutely certain our specific sample mean is the same as the population mean?

no, there's always the possibility of sampling error

Which assumptions below apply for an independent samples t test? Choose all that apply. (Assume you have a small sample.)

normally-distributed populations equal variances for each group

A desperate statistician believes that using corny stats jokes as pick-up lines will increase the number of dates he goes on. Statisticians, as a group, typically go on 1.3 dates per year, σ = 0.4 To test whether the statistician is correct, would you use a one-tailed test or two-tailed?

one

When cases are not selected independently of one another and share certain characteristics, those samples are:

related

The _____ provides an overall average of how far different sample means deviate from the true population mean.

standard error of the mean

As alpha increases, what happens to the likelihood of rejecting the null hypothesis?

the likelihood increases

The t test statistic for related samples is a ratio of mean differences relative to

the standard error of the mean difference.

Why do we use μ D ¯ when we write hypotheses about mean differences?

the symbol μ means "hypothesis" in Greek.

With hypothesis testing, whether a conclusion is actually true or not is unknown, though we can calculate how likely it is that a conclusion is true.

true

A ___ - tailed hypothesis is also known as a non-directional hypothesis.

two

A sampling distribution of mean differences that represents the null hypothesis will be centered on ____ . (Or in other words, what value will be at the center/middle of the sampling distribution of means.)

zero