Chapter 11

A two tailed t-test was constructed for x-bar=52, sx-bar=4 and population mean =52. tcrit=2.086 was determined. Assuming your test is significant what is the correct 95% confidence interval for the population mean?

(43.656, 60.344)

A study with 46 participants investigated whether there was a relationship between one's attitude toward giving blood and the number of times one has given blood in a year. The correlation coefficient was r=+0.56. The rcrit is _____ and the investigator should ____

+- 0.288; reject H0

If a sample mean has a value equal to the population mean, the corresponding value of t will be equal to

0.0

What does the tobt value indicate?

How far the sample mean is from the population mean of the sampling distribution in estimated standard error units.

Degrees of freedom for the one-sample t-test is equal to

N-1

How many degrees of freedom do we have in significance testing of r?

N-2, where N equals the total number of pairs of scores.

Which of the following statements about the correlation coefficient is true?

One should not accept that a correlation coefficient represents a relationship unless it is significant.

Which kind of estimation is performed when we claim that a population mean is equal to the sample mean?

Point estimation

The logic behind computing a confidence interval is to compute the highest and lowest possible values of a_____ mean that are not significantly different from those of _____.

Population; the current sample mean.

How is the t-distribution defined?

The distribution of all possible values of t for random samples having the same N from the population described by H0

What is Sx(bar)?

The estimated standard error of the mean.

Which of the following is one of the assumptions of a one-sample t-test?

The population standard deviation is estimated by computing sx

What happens to the t-distribution as the sample size increases?

The t-distribution appears more and more like a normal distribution.

Suppose you correlation reading levels with the ages of 30 elementary school children. You compute robt and find it to be 0.72, which is a significant correlation coeffiient. Which of the following is the most appropriate conclusion?

There is a positive relationship between age and reading level that exceeds chance expectations.

Which of the following assumptions is common to both the z-test and the one sample t-test?

There is one random sample of interval or ration scores.

Which of the following is one of teh assumptions for hypothesis testing of the Pearson correlation coefficient?

There is random sampling of X-Y pairs.

What is the purpose of using a confidence interval?

To use a sample mean to estimate the value of a population mean

If all other factors are held constant, increasing the level of confidence will have what kind of effect on the width of a confidence interval?

increase it

The process of specifying a range of values within the population parameter is estimated to fall is known as

interval estimation.

The major problem with point estimation is that is

is extremely vulnerable to sampling error.

The null hypothesis in a two-tailed signigicance test of crrelation states that

no correlation exists in the poulation.

When we construct a 95% confidence interval, we are 95% sure that the

population mean falls within the interval.

Suppose you perform a two-tailed significance test on a correlation using 29 participants. Your robt is 0.56, which is a significant correlation coefficient. Which of the following is the correct way to report this finding?

r(27)=0.56, P<0.05

In a study involving 22 participants, you have found that the Pearson correlation coefficient between the amount of Chemical J2 and roller coaster enjoyment is 0.53. Use a two-tailed test and a=0.01 to determine if this is a significant correlation coefficient.

rcrit=0.537, p>0.01

Suppose you conduct an experiment with 24 subjects and your tobt turns out to be 2.92, which is statistically significant. Which of the following is the correct way to report the results?

t(23)=2.92, p<0.05

Unless we use the correct tcrit from the t-distribution for the appropriate N,

the probability of making a Type I error will not equal a.

A developmental psychologist interested in the development of color perception presented 20 one-month-old infants with a pair of color forms. One form had two colors and the other ahd one. If the infants perferred to look at the form with two colors above chance level (50%), they can perceive colors. The mean percentage of times the infants perferred the two-color form was 53.15 (S^2x=14.345). What is tobt?

3.72

Using the data given below, perform a two-tailed t-test to compare the sample mean to the population mean=35.5. use a=0.05. 38, 40, 41, 37, 35, 38, 41, 39, 34, 35, 38, 42, 44, 37

3.90>2.16, p<0.05

A two-tailed t-test was conducted for x-bar=97, sx-bar=5, N=21 and the population mean =100. Using a=0.05, tcrit=2.086 was compared to tobt what is the correct 95% confidence interval for the population mean?

A confident interval should not be constructed because the t-test is not significant.

When establishing the proper confidence interval for interval estimatino, which of the following should be employed?

A two-tailed value of tcrit

If a researcher reports a one-sample t-test with df=12, how many individuals participated in this study?

13

In a on-sample t-test with 18 participants how many degrees of freedom are there?

17

For X-bar=52, sx=3, N=20, and the population mean=50, tobt=_____ and tcrit=_____ for a two-tailed test with a=0.05

2.981;2.093

Which of the followign would increase the power of a significance test for correlation?

Changing the sample size from N=25 to N=100

Which of teh followign would increase the power of a t-test?

Chanign the sample size from N=25 to N=100

When us a t-test used instead of a z-test?

When the population standard deviation is unknown

The alternative hypothesis in a two-tailed significance test of correlation states that

a correlation exists in the population.

If we reject the null hypothesis in a significant test of correlation, we conclude that there is

a nonchance relationship between the X and Y variables.

The confidence interval for a single m is

an interval containing values of m that our sample mean is likely to represent.

What happens to the power of a t-test when the variability of the raw scores is increased? The power will

decrease.

What happens to the absolute value of tcrit as df increases? it

decreases

What does the shape of any particular sampling distribution of a correlation coefficient depend upon?

df

For a two-tailed test with a=0.05, the tcrit value is

different for each df