Topic: Drawing Inferences (Two Sample)

Problem 1:

A psychologist studying the human factors of computer keyboards sets - up an experiment to compare two different keyboard designs. He measures the number of words per minute typed by one group on Keyboard A and then he measures the number of words typed per minute by another group of people on Keyboard B. Use the data below to determine if the typing speeds on the two different keyboards are significantly different.

Keyboard A (words per minute)	Keyboard B (words per minute)
54, 62, 75, 59, 78, 64, 69, 72, 50, 73	47, 51, 54, 62, 44, 51, 48, 65, 42, 44, 71, 68

Problem 2:

A research study was conducted to examine the differences between older and younger adults on perceived life satisfaction. A pilot study was conducted to examine this hypothesis. Ten older adults (over the age of 70) and ten younger adults (between 20 and 30) were given a life satisfaction test (known to have high reliability and validity). Scores on the measure range from 0 to 60 with high scores indicative of high life satisfaction and low scores indicative of low life satisfaction. The data are presented below and test if there issignificant difference between the perceptions of the respondent groups.

Older Adults	Younger Adults
45,38, 52, 48, 25, 39, 51, 46, 55, 46	34, 22, 15, 27, 37, 41, 24, 19, 26, 36

Problem3:

One group of 6 participants was shown a movie on the evils of alcohol use and the other group of 7 participants was shown a movie about dog nutrition. Both groups were then given a test measuring their attitude toward drug use. The scores for both groups are listed below (high scores indicate a resistance to the use of drugs).

Alcohol Movie	Dog Movie
132, 144, 131, 145, 156, 139	121, 130, 122, 125, 119, 100, 105

Problem 4:

A researcher has just finished a research project using 8 anorexia nervosa patients as participants. She was testing the effectiveness of a particular type of psychotherapy on these patients. Below is listed the weights of the 8 patients before and after the therapy.

Weight Before	Weight After
67, 74, 79, 77, 82, 69, 54, 99	74, 92, 88, 92, 77, 82, 84, 99

Problem 5:

The researcher wants to compare ground versus air-based temperature sensors to determine the earth's temperature, which is important for agricultural modeling, etc. Ground-based sensors areexpensive, and air-based (from satellites or air-planes) of infrared wavelengths may be biased. Matching the temperature data, test if they are different.

Ground	Air
46.9, 45.0, 36.3, 31.0, 24.7,22.3, 49.8, 40.5, 37.7, 35.0	47.3, 48.1, 37.9, 32.7, 26.2, 23.3,50.2, 42.6 , 39.4 , 37.9

Problem 6:

Is there a difference in marks following a teaching intervention? The marks for a group of students before (pre) and after (post) a teaching intervention are recorded below:

Pre - test	Post - test
18, 21, 16, 22, 19, 24, 17, 21, 23, 18,14, 16, 16, 19, 18, 20, 12 ,22, 15	22, 25, 17, 24, 16, 29, 20, 23, 19, 20,15, 15, 18, 26, 18, 24, 18, 25, 19

Problem 7:

Two machines fill bottles of water. Each machine performance is checked periodically testing bottles removed randomly from the production line and yield the following statistics:

Machine	Mean Weight	Standard Deviation	Number of Bottles Taken
1	203.56	3.56	40
2	200	2.02	50

Use the 6 steps procedure to arrive at a decision from a 0.01 alpha level.