Question

State the null and alternative hypotheses for each conjecture.

a. A researcher thinks that if expectant mother use vitamin pills, the birth weight of the babies will increase. The average birth weight of the population is 8.6 pounds.

b. An engineer hypothesizes that the mean number of defects can be decreased in a manufacturing process of compact disks ny using robots instead of humans for certain tasks. The mean number of defective disks per 1000 is 8.

c. A psychologist feels that playing soft music during a test will change the results of the test. The psychologist is not sure whether the grades will be higher or lower. In the past, the mean of the scores was 73.

Answer 1

(a): In the study, the researcher wants to check whether the birth weight of the babies will increase if the expectant mother use vitamin pills.

It is given that the average birth weight of the population is 8.6 pounds.

Let be the average birth weight of the population.

The null and alternative hypothesis can be framed as:

It is a right tailed test.

(b): In the study, the engineer hypothesizes that the mean number of defects can be decreased in a manufacturing process of compact disks by using robots instead of humans for certain tasks.

It is given that the mean number of defective disks per 1000 is 8.

Let be the mean number of defective disks per 1000.

The null and alternative hypothesis can be framed as:

It is a left tailed test.

(c): In the study, a psychologist feels that playing soft music during a test will change the results of the test (grades will be either higher or lower).

It is given that the mean of the scores in the past was 73.

Let be the mean of the scores in the past.

The null and alternative hypothesis can be framed as:

It is a two-tailed test.