2. Formulating hypotheses and determining whether a test is one-or two-tailed

To identify the correct Z(critical), it is important to determine whether the hypothesis test is one-tailed or two-tailed. The decision between a one- and two-tailed hypothesis is based on the researcher's expectations about the population from which the sample was selected.

Many people believe that millennials are having more sex than people during the sexual revolution. You wonder whether the cohort currently in their mid-20s have had more sexual partners than older generations. Assume that the the average number of sexual partners by age 25 is 4.2 partners. You obtain a sample that yields a sample mean of X

= 6.5 partners.

Let denote the average number of sexual partners by age 25. Formulate your null and research hypotheses by selecting the appropriate values in the dropdown menus that follow.

H0

:
(H1

:

The test you conduct is a test.

Note: A one-tailed test is described as a lower-tailedtest if the null hypothesis is rejected for values of the test statistic in the lower tail of its distribution, and it is described as an upper-tailedtest if the null hypothesis is rejected for values of the test statistic in the upper tail of its distribution.

Use the distribution tables to complete the exercises that follow.

0.0000 Area Beyond Z 0.0013

0.0014 Area Beyond Z 0.0062

0.0064 Area Beyond Z 0.0228

0.0233 Area Beyond Z 0.0668

0.0681 Area Beyond Z 0.1587

0.1611 Area Beyond Z 0.3085

0.3121 Area Beyond Z 0.5000

(a)	(b)	(c)		(a)	(b)	(c)
Z	Area Between Mean and Z	Area Beyond Z		Z	Area Between Mean and Z	Area Beyond Z
3.00	.4987	.0013		3.30	.4995	.0005
3.01	.4987	.0013		3.40	.4997	.0003
3.02	.4987	.0013		3.50	.4998	.0002
3.03	.4988	.0012		3.60	.4998	.0002
3.04	.4988	.0012		3.70	.4999	.0001
3.05	.4989	.0011		3.80	.4999	.0001
3.06	.4989	.0011		3.90	.5000	.0000
3.07	.4989	.0011		4.00	.5000	.0000
3.08	.4990	.0010
3.09	.4990	.0010
3.10	.4990	.0010
3.11	.4991	.0009
3.12	.4991	.0009
3.13	.4991	.0009
3.14	.4992	.0008
3.15	.4992	.0008
3.16	.4992	.0008
3.17	.4992	.0008
3.18	.4993	.0007
3.19	.4993	.0007
3.20	.4993	.0007
3.21	.4993	.0007
3.22	.4994	.0006
3.23	.4994	.0006
3.24	.4994	.0006

Using the significance level of p = 0.05, the critical value(s) for a test of the previously stated null hypothesis is/are .