The waiting time for customers at Walton Shopping Mall chains follows a normal distribution with a mean of 3 minutes and a standard deviation of 1 minute. At the Brooklyn Mall, the quality-assurance department sampled 50 customers and found that the mean waiting time was 2.75 minutes. At the 0.05 significance level, can we conclude that the mean waiting time is less than 3 minutes? Based on this, which of the following is true:
a. p = 0.0174, We conclude that the mean waiting time is not less than three minutes
b. p = 0.4616, We conclude that the mean waiting time is less than three minutes.
c. p = 0.4616, We conclude that the mean waiting time is not less than three minutes.
d. p = 0.0384, We conclude that the mean waiting time is less than three minutes.
e. p = 0.0384, We conclude that the mean waiting time is not less than three minutes.
A normal population has a mean of 60 and standard deviation of 12. A random sample of 9 is selected. The probability that the sample mean is less than 56 is:
a. 0.4136
b. 0.6147
c. 0.1587
d. 0.3413
e. 0.3285
A group of statistics students decided to conduct a survey at their university to find the average (mean) amount of time students study per week. Based on a simple random sample, they surveyed 144 students. The statistics showed that students studied an average of 20 hours per week with a standard deviation of 10 hours. What is the probability of finding a sample mean less than 18 hours?
a. 0.0181
b. 0.4918
c. 0.4820
d. 0.2133
e. 0.0082
An accounting firm is planning for the next tax preparation season. From last year's returns, the firm collects a systematic random sample of 100 filings. The 100 filings showed an average preparation time of 90 minutes with a standard deviation of 140 minutes. What is the standard error of the mean?
a. 14 minutes
b. 90 minutes
c. 1.4 minutes
d. 140 minutes
If we use a population consisting of the following values of 2, 2, 4, 4, and 8, and take samples of size two from that population, comparing the dispersion in population with that of sample means, we can say that:
a. None is correct
b. The population varies from 2 to 8, whereas the sample means only vary from 2 to 6.
c. The population varies from 2 to 8, whereas the sample means only vary from 2 to 10.
d. The population varies from 2 to 8, whereas the sample means only vary from 2 to 12
e. The population varies from 2 to 8, whereas the sample means only vary from 2 to 4.
A sample of 36 observations is selected from a normal population. The sample mean is 49, and the population standard deviation is 5. Conduct the following test of hypothesis using the 0.05 significance level. If we want to test the hypothesis that the mean is equal to 50, therefore
a. The decision would be to reject H0 on the basis of p-value of 0.123
b. The decision would be not to reject H0 on the basis of p-value of 0.123
c. The decision would be not to reject on the basis of p-value of p = 0.2302
d. None is correct
e. The decision would be not to reject on the basis of p-value of p = 0.0903
From a population consisting of the following values of 2, 2, 4, 4, and 8, how many samples of size two can be drawn?
a. 13
b. 12
c. 9
d. 10
e. 11
If the alternate hypothesis states that µ does not equal 4,000, what is the rejection region for the hypothesis test?
a. Center
b. Upper or right tail
c. Both tails
d. Lower or left tail
If the critical z-value for a test statistic equals 2.45, what value of the test statistic would provide the least chance of making a Type I error?
a. 4.56
b. 10,000
c. 5.63
d. 3.74
e. 2.46
A random sample of size 15 is selected from a normal population. The population standard deviation is unknown. Assume that a two-tailed test at the 0.10 significance level is to be used. For what value of t will the null hypothesis not be rejected?
a. To the left of -1.282 or to the right of 1.282
b. To the left of -1.345 or to the right of 1.345
c. None is correct
d. To the left of -1.645 or to the right of 1.645
e. Between -1.761 and 1.761
According to the central limit theorem,
a. The sampling distribution of the sample means is approximately normally distributed.
b. The sampling distribution of the sample means will be skewed.
c. None is correct
d. Increasing sample size decreases the dispersion of the sampling distribution
e. The population mean, and the mean of all sample means are equal