Chapter 1, Problem 12TY

Summary Introduction

Introduction:

Predictions and hypotheses are often tested using carefully designed experiments. These experiments need to be controlled experiments. This essentially means that no other variable, apart from the one being tested for, must affect the outcome. The variables involved can be independent variables or dependent variables. Independent variables are those which stand alone and are not changed by the variable we wish to measure. These include time, age, distance, drug treatment, and no drug treatment. Dependent variables are those which are dependent on an independent variable. Examples are growth or blood pressure. Experiments are designed in a way so that only one independent variable is manipulated or controlled.

An experiment designed to test the effectiveness of a drug would start with picking a large number of suitable subjects for that experiment. These are then randomly divided among experimental and control groups. Everything else for both the groups is kept exactly the same apart from the controlled variable, which is the administration of the drug. Experimental group would get the drug and control group would receive an identical pill but with no drug which is the placebo. The results of the two groups are then compared to see the effect of the drug.