Question

A random selection of volunteers at a research institute have been exposed to a typical cold virus. After they started to have cold symptoms, 10 of them were given multivitamin tablets daily which contain 3 grams of vitamin C and various other vitamins and minerals. The remaining 10 volunteers were given placebo tablets. For each individual, the length of time taken to recover from cold is recorded. At the end of the experiment following data are obtained:

Days to recover from cold Treated with multivitamin 7.6, 4.5, 8.9, 4.5, 4.8, 4.6, 8.5, 5.7, 8.1, 4.6

Treated with placebo 6.8, 6.6, 3.1, 4.5, 7.6, 4.3, 5.1, 5.4, 6.8, 5.5

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It is known that the population standard deviation of recovery time from cold is 1.8 days when treated with multivitamin, and the population standard deviation of recovery time from cold is 1.5 days when treated with placebo tablets. It is also known that both populations are approximately normally distributed. The researchers claim that the mean recovery time,µ1 , of the patients treated with multivitamin is not equal to the mean recovery time µ2, of the patients who are treated with placebo tablets. At the level 0.01 of significance, is there enough evidence to support this claim? Perform a two-tailed test. Then fill in the table below.

Carry your intermediate computations to at least three decimal places and round your answers as specified in the table.

The null hypothesis: The alternative hypothesis:

The type of test statistic:

The value of the test statistic: (Round to at least three decimal places.)

The p-value: (Round to at least three decimal places.)

Can we support the researchers' claim that the mean recovery time when treated with multivitamin is not equal to the mean recovery time when treated with placebo?

Answer 1