Final answer:
In a study examining the effects of exercise type on weight loss, the independent variable is the exercise regimen, and the dependent variable is weight loss. There should be about 30 people in each exercise group. Sample bias, ratio scale for weight measurement, and the formulation of null and alternative hypotheses are other important aspects discussed.
Step-by-step explanation:
Variables in an Exercise and Weight Loss Study
The independent variable in this study is the type of exercise regimen, which includes pure cardio, pure weight training, and a combination of the two. The dependent variable is the amount of weight loss experienced by the subjects, as this is the outcome that the researcher is interested in measuring and is expected to change in response to the different types of exercise interventions.
As 90 people are randomly assigned to three different exercise regimens, approximately 30 people should be in each group to ensure an even distribution and a balanced experimental design.
One potential source of sample bias might be if individuals in the study had varying levels of previous exercise experience or different metabolic rates, as these factors could affect their weight loss outcomes.
Weight loss is measured on a ratio scale, as it has a true zero point (no weight loss), and the differences and ratios between measurements are meaningful.
The null hypothesis for this study would likely be that there is no difference in weight loss among the three different exercise regimens, while the alternative hypothesis would posit that there is a significant difference in weight loss between at least two of the exercise regimens.