In testing the difference between two population means using two independent samples, the population standard deviations are assumed to be known and the calculated test statistic equals 2.56 . If the test is two-tail and 5 level of significance has been specified, the conclusion should be to:
a. reject the null hypothesis
b. not to reject the null hypothesis
c. repeat using a one-tail test
d. choose two other independent samples
e. none of these
Q. 2If the standard normal deviate of a random variable value of x = 2 is z = 2, while the standard deviation of the random variable x equals 2, then the mean of x is:
a. 6
b. 4
c. 8
d. 2
e. 0
Q. 3If you wish to estimate the difference between two population means using two independent large samples, the 90 confidence interval estimate can be constructed using which of the following critical values?
a. 1.96
b. 2.33
c. 2.58
d. 1.645
e. 1.28
Q. 4Given a normal distribution with a mean of 80 and a standard deviation of 20, an observation of x = 50 corresponds to a standard normal deviate:
a. of z = +1.5
b. of z = +3.0
c. of z = 1.5
d. of z = 3.0
e. of none of these
Q. 5If you wish to construct a confidence interval estimate for the difference between two population means, an increase in the sample sizes used will result in:
a. a decrease in the critical value z
b. a narrower confidence interval
c. a wider confidence interval
d. a confidence interval that contains zero
e. a confidence interval that does not contain zero
Q. 6Members of the normal probability distribution family differ from one another only by:
a. mean and standard deviation
b. median and standard deviation
c. mode and standard deviation
d. any of these
e. none of these
Q. 7When testing for differences between the means of two dependent populations, we can use either a one-tailed or two-tailed test.
Indicate whether the statement is true or false
Q. 8Which of the following correctly describes the normal probability distribution?
a. It is single-peaked above the random variable's mean, median, and mode, all of which are equal to one another.
b. It is perfectly symmetric about this peaked central value and, thus, said to be bell-shaped.
c. It features tails extending indefinitely in both directions from the center, approaching (but never touching) the horizontal axis, which implies a positive probability for finding values of the random variable anywhere between minus infinity and plus infinity.
d. All of these.
e. None of these.
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