For the following situations, please name the most appropriate statistical test

Question

For the following situations, please name the most appropriate statistical test from among those that you have learned. Briefly state why it is the most appropriate. Also state whether a one- or two-sided test is more appropriate. Briefly state why it is more appropriate.

a) A study was designed to test the effects of a new public health ad campaign. A representative random sample of people who had seen the ads, and another representative random sample of people who had not seen the ads were collected. The goal was to determine whether there is a difference between these two groups on attitude towards drug use. The measure for attitude is a 5-point ordinal scale that ranges from “strongly negative” to “strongly positive”.

b) A study was conducted to compare the water supply among four different communities in Africa. For each community, 100 water samples were obtained and the level of E. coli in each sample was measured as a continuous variable. The investigators were interested in determining if a difference existed among the four communities.

c) A study was designed to determine whether there is an association between the occurrence of iron deficiency in women and their level of education. Women were divided into two groups: those with less than or equal to 12 years of education and those with greater than 12 years of education. They also were divided into deficient or normal based on the established clinical normal range.

d) A study was designed to determine the effect, if any, of a certain disease on plasma potassium levels. Plasma potassium levels can be assumed to be normally distributed. Investigators were interested in knowing whether diseased individuals had higher blood levels than normal individuals. A sample of individuals with disease was compared with a sample of individuals without the disease.

Explanation / Answer

a) Two sample t-test(Two-sided test):

H0: If the mean attitude towards drug from two groups is equal

Ha: If the mean attitude towards drug usage is not equal

The difference between two groups can be strongly positive or strongly negative. So, there is a chance going low or high.

b) One way ANOVA- F test(Two-sided test):

H0: If all four groups means are equal

Ha: If at least one group is not equal

While differentiating the group means, we are not sure of the values might vary as high or low. So, we have to use two-sided test.

c) Two-sample t-test(Two-sided test):

H0: if both groups are equal to iron deficiency

Ha: if both groups are not equal to iron deficiency

Those less than or equal 12 years of education and those with greater than 12 years of education, calculating the difference of iron deficiency.

d) Two sample t-test(One-sided test):

H0: If diseased individuals and normal individuals have same BP

Ha: If diseased individuals had higher BP levels than normal individuals

We are interested in calculating the value that, BP is high on diseased people than normal people.

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