MSA622 EXAM 2 (CH 11)
In a sample of eight participants, a researcher estimates the 95% CI for a sample with a mean of M = 15 and an estimated standard error for the difference scores of 5.35. What is the confidence interval at this level of confidence?
Answer = 95% CI 2.35, 27.65
Lower Confidence Limit
The smallest possible value of a population parameter in a confidence interval with a specified level of confidence
Level of Confidence
The probability or likelihood that an interval estimate will contain an unknown population parameter
What is the 2-tail level of significance that corresponds with the following levels of confidence. a. 99% b. 95% c. 90% d. 80%
a) .01 b) .05 c) .10 d) .20
Confidence Boundaries
The upper and lower boundaries of a confidence interval given within a specified level of confidence; also called confidence boundaries
Confidence Limits
The upper and lower boundaries of a confidence interval given within a specified level of confidence; also called confidence boundaries
In a sample of 18 participants, a researcher estimates the 95% CI for a sample with a mean of M = 8.8 and an estimated standard error for the difference of 1.8. What is the lower confidence limit for this interval?
Answer = 5.0
A researcher surveys the amount of caffeinated drinks consumed by 12 participants and estimates the 80% CI for a sample with a mean of M = 22.3 and an estimated standard error of 4.7. What is the confidence interval at this level of confidence?
Answer = 80% CI, 15.9, 28.7
Confidence Interval (CI)
he interval or range of possible values within which an unknown population parameter is likely to be contained
The confidence interval for one sample selected from a population with an unknown variance is computed using a critical value for which type of test?
t test
Which of the following explains why interval estimation can be a useful procedure to estimate a population mean?
it defines the range of scores within which the population mean is likely to be contained
A statistical procedure in which a sample mean is selected to determine the likelihood of obtaining that mean if the null hypothesis were true is:
significance testing
The estimated standard error for the difference is used to compute the confidence interval for which test?
z test
The z score for a 90% confidence interval is:
+/- 1.645
What is 1 advantage and 1 disadvantage of using "point estimate" to estimate a population mean?
1. advantage: point estimate is an unbiased estimator of the population mean 2. disadvantage: we have no way of knowing for sure weather a sample mean equals the population mean
What is the estimation formula for a one-sample t test?
M=/-t(sm)
Increasing the level of confidence increases the certainty of an estimate, T/F? (Textbook p.355)
True
What are 2 types of estimates for the population mean?
1. point estimate 2. interval estimate
What is the difference between the 1). precision and 2).certainty of a confidence interval?
1. precision of an estimate is determined by the range of the confidence interval 2. certainty of an estimate is determined by the level of confidence
When the null hypothesis is outside a confidence interval, this indicates that it would likely be rejected with hypothesis testing, T/F?
True
Interval Estimation
A statistical procedure in which a sample of data is used to find the interval or range of possible values within which a population parameter is likely to be contained
Estimation
A statistical procedure in which a sample statistic is used to estimate the value of an unknown population parameter. Two types of estimation are point estimation and interval estimation
Point Estimation
A statistical procedure that involves the use of a sample statistic to estimate a population parameter
For the same data, decreasing the certainty of an estimate will result in a less precise estimate, T/F?
False
The "Upper confidence" level is the largest possible value of a standard error in a specified confidence interval, T/F?
False
A researcher increases her level of confidence from 95% to 99%. What will happen to the precision of her estimate?
The estimate will be less precise
The goal of ______ is the same as that in hypothesis testing: to learn more about the value of a mean or mean difference in a population of interest.
estimation
The estimated standard error for the difference is used to compute the confidence interval for which test?
two-independent sample
Upper Confidence Limit
The largest possible value of a population parameter in a confidence interval with a specified level of confidence Definition 9 of 9
What are 2 rules for the precision and certainty of a confidence interval (CI)?
1. decreasing the level of confidence increases the precision of an estimate 2. increasing the level of confidence increases the certainty of an estimate
What is the t(Smd) for a 95% confidence interval given that nd = 4 and Sd = 8? (Textbook p.354)
Answer = t(Smd) = 3.182 x 8/sq root 4 (for the steps refer to CH 14 slides they help)
What are the 3 steps to estimate the value of a population mean using a point estimate and an interval estimate?
Step1: Compute the standard mean & Standard error Step2: Choose level of Confidence & critical value Step3: Compute the estimation formula & find confidence limits
Research has found that the average IQ in the U.S. is 100 points, which is a point estimate. is this T/F?
True
To estimate the population mean for the related-samples t, the estimated standard error of the difference scores must be known, T/F?
True
A population mean falls between these limits a)________ and b)__________?
a. point estimate and b. interval estimate
