Identify whether the studies described here are based on (1) single samples, (2) paired samples, or (3) independent samples.

a. An investigator compares vaccination histories in 30 autistic schoolchildren to a simple random sample of non-autistic children from the same school district.

b. Cardiovascular disease risk factors are compared in husbands and wives.

c. A nutritional exam in applied to a random sample of individuals. Results are compared to expected means and proportions.

a. Study: To compare vaccination histories in 30 autistic schoolchildren with a simple random sample of non-autistic children from the same school district.

The studies are based on two independent samples

In this, the first sample is a group of autistic children and other is a group of non-autistic children. The variable under study being vaccination histories.

Moreover, the two samples are not dependent on others.

b. Study: Cardiovascular disease risk factors are compared in husbands and wives.

The study is based on paired samples

In this, the first sample is a group of husbands and other being the group of wives. The two groups are paired as each individual in the first group is related to an individual in another group (husband-wife pair).

c. Study: A nutritional exam is applied to a random sample of individuals.

The study is based on one sample

In this, there is only one group of individuals being examined for a nutritional exam. The variable in this study is a nutritional exam score.