Question

In each of the following instances (i) tell whether the study is experimental or observational, (ii) tell whether the study is comparative or descriptive, and (iii) if the study is comparative, identify the response and explanatory variables.

a) Annual rates of return on investment are compared among different groups of mutual founds.

b) In a pilot phase of fund-raising campaign, a university randomly contacts half of a group of alumni by telephone and the other half by a personal letter from the chair of the alumnae’s department to determine which methods results in a larger proportion of contributors.

c) To analyze possible problems from the by-products of gas combustion, women with respiratory problems (e.g., wheezing asthma) are matched by age to women without respiratory problems and then asked whether or not they cook on a gas stove.

d) An industrial pump manufacturer monitors warranty claims and surveys customers to assess the failure distributions of its pumps.

Answer 1

a) (i) Observational because we are not intervening into the process but merely taking observations after the process is already done. (ii) comparative since comparison is being done among participants. (iii) response : Annual return of mutual fund group ; explanatory : type of mutual fund group

b) (i) Experimental because we are intervening in the process and collecting data. (ii) Comparative because two methods are being compared (iii) Response : Proportion of contributors ; Explanatory : Method of fund raising

c) (i) Observational because process is over and after that we are collecting data. (ii) Comparative because based on cooking method used, women are surveyed. (iii) Response : Existence of respiratory problems   ; Explanatory : Type of cooking method (Gas stove or not)

d) (i) Observational because only observations are monitored but no intervention is done in the process. (ii) Descriptive because we just want to describe the failure distribution of pumps.