Question

1. Confidence intervals for mean differences provide researchers with

	a.	the probability that a given result would occur in the null hypothesis is true.
	b.	the degree to which a treatment changed a DV in standard deviation units.
	c.	a range of plausible population values if a study were applied to an entire population.
	d.	the typical distance between sample means and a population mean.

2. Is the following statement true? Values between the LB and UB values of a 95% CI are all equally plausible values for a population parameter.

	a.	True
	b.	False
	c.	it depends, this is true if the CI is for a population mean difference
	d.	it depends, this is true if the CI is for a population mean

3. When computing a 95% CI for a population mean the ______ is used to compute the margin of error.

	a.	two-tailed .05 t-value based on sample size and the SEM
	b.	the one-tailed .05 t-value based on sample size and the SEM
	c.	the difference between the LB and UB and the SEM
	d.	the difference between the LB and UB.

4. M = 28; SD = 4; N = 49; you need a 95% CI to estimate a population mean. What is the point estimate?

	a.	95
	b.	28
	c.	49
	d.	.57

5. M = 28; SD = 4; N = 49; you need a 95% CI to estimate a population mean. What is the margin of error?

	a.	1.149
	b.	2.0106
	c.	.57
	d.	.164

6. M = 28; SD = 4; N = 49; you need a 95% CI to estimate a population mean. What is the UB?

	a.	29.149
	b.	30.0096
	c.	28.57
	d.	28.164

7. M = 28; SD = 4; N = 49; you need a 95% CI to estimate a population mean. What is the LB?

	a.	26.85
	b.	25.9904
	c.	27.43
	d.	27.836

Answer 1

1) Confidence intervals for mean differences provide researchers with

c.

a range of plausible population values if a study were applied to an entire population.

EXPLANATION: Confidence interval is a range of values for the population parameter based on sample.

2) Values between the LB and UB values of a 95% CI are all equally plausible values for a population parameter.

a.

True

EXPLANATION: Confidence interval is a range of values for the population parameter based on sample.

3) When computing a 95% CI for a population mean the_________is used to compute the margin of error.

a.

two-tailed .05 t-value based on sample size and the SEM

Explanation: MOE= tc*s/sqrt(n)

where tc is critical value based on sample size and s/sqrt(n) is standard error of mean.

4) Sample mean is point estimate of population mean therefore it is 49 OPTION C

5) MARGIN OF ERROR= tc*s/sqrt(n)

MOE= 2.01*4/sqrt(49)

= 2.01*4/7

= 1.149 OPTION A

6) UPPER BOUND= xbar+MOE= 28+1.149= 29.149 OPTION A

7) LOWER BOUND= xbar-MOE= 28-1.149= 26.85 OPTION A