Exam 10: A: Inference From Small Samples

Suppose that a t test is being conducted at the 0.05 level of significance to test vs. . A sample of size 20 is randomly selected. What is the rejection region?

A race car driver tested his car for time from 0 to 60 mph, and in 20 tests obtained an average of 48.5 seconds with a standard deviation of 1.47 seconds. A 95% confidence interval for the 0 to 60 time is 4.52 seconds to 5.18 seconds.

In testing vs. the larger the sample sizes from the two populations, the smaller will be the chance of committing a Type I error.

In a paired-difference experiment, two samples of size n are being used. The number of degrees of freedom associated with the paired-difference test is n - 1.

Two independent samples of sizes 25 and 35 are randomly selected from two normal populations with equal variances. In order to test the difference between the population means, which of the following would best describe the test statistic?

Based on sample data, the 90% confidence interval limits for the population mean are LCL = 170.86 and UCL = 195.42. If the 10% level of significance were used in testing the hypotheses vs. , what would you conclude?

The number of degrees of freedom associated with the t test when the data are gathered from a matched pairs experiment with 8 pairs is 7.

Which of the following best describes the sampling distribution of the ratio of two independent sample variances selected randomly from normal populations with equal variances?

What is the number of degrees of freedom associated with the t test when the data are gathered from a matched pairs experiment with 10 pairs?

If a sample of size 15 is randomly selected from a population, the value of A for the probability P(t A) = 0.01 is 2.602.

The statistic ) when the sampled population is normal is the Student's t distributed with n degrees of freedom.

The necessary conditions having been met, a two-tailed test was conducted to test the difference between two population means. However, the statistical software provided only a one-tailed area of 0.045 as part of its output. In this case, the p-value for this test would have been 0.09.

A researcher is curious about the effect of sleep on students' test performances. He chooses 50 students and gives each two tests: one given after four hours of sleep and one after eight hours of sleep. The test the researcher should use would be a matched pairs t test.

The Student's t distribution is used to construct confidence intervals for the population mean when the population standard deviation is known.

In testing the difference between two population means using two independent samples, under which of the following conditions would we use the pooled variance in estimating the standard error of the sampling distribution of the sample mean difference ?

For a t distribution with 12 degrees of freedom, the area between -2.6810 and 2.1788 is 0.980.

We can use either the z test or the t test to determine whether two population variances are equal.

A right-tailed area in the chi-square distribution equals 0.05. For eight degrees of freedom, the critical value equals 13.362.

In a hypothesis test for the population variance, the hypotheses are vs. . The sample size is 20 and the test is being carried out at the 5% level of significance. Under which of the following conditions would the null hypothesis be rejected? A) B) C) D)

With all other factors held constant, confidence intervals constructed with small samples tend to have greater margins of error than those constructed from larger samples.