Chapter 4, Problem T4.14SPT

(a)

To determine

To identify the explanatory and response variables in this experiment.

Answer to Problem T4.14SPT

Explanatory variable: The treatment given (caffeine capsule or placebo).

Response variable: The time it takes to complete the tapping task.

Explanation of Solution

In an experimental study, the explanatory variable is the variable that is manipulated by the researcher. Explanatory Variable is also known as the independent or predictor variable, it explains variations in the response variable.

Thus, in this case,

Explanatory variable: The treatment given (caffeine capsule or placebo)

And the Response variable: The time it takes to complete the tapping task.

(b)

To determine

To explain how was blocking used in the design of the experiment and what was the benefit of blocking in the experiment.

Explanation of Solution

Blocking was used in this experiment as each of the $11$ individuals will be a block in a matched pairs design. Each participant will take the caffeine tablets on one of the two-day sessions and the placebo on the other. The blocking was done to account for individual differences in dexterity.Blocking is used to remove the effects of a few of the most important nuisance variables. Randomization is then used to reduce the contaminating effects of the remaining nuisance variables. For important nuisance variables, blocking will yield higher significance in the variables of interest than randomizing.

(c)

To determine

To explain what problem does confounding caused.

Explanation of Solution

The problem confounding caused is that after the first trial, subjects might practice the tapping task and do better the second time, If all the subjects got caffeine the second time, the researches would not know if the increase was due to the practice or the caffeine.

(d)

To determine

To explain could this experiment have been carried out in a double-blind manner or not.

Answer to Problem T4.14SPT

Yes it could be.

Explanation of Solution

Yes,this experiment could have been carried out in a double-blind manner if neither the subjects nor the people who come in contact with them during the experiment (including those who record the number of taps) have knowledge of the order in which the caffeine or placebo was administered.