Manipulative skills

Use this page to explain that we are interested in the difference between the groups and, in particular, the difference between the group means, . However this difference is random, so we must understand its distribution before we can interpret its value.

The simulation is based on a real data set, but only mention that the difference between the model's group means is µ2  - µ1 = 2.20 pins. Take several samples and mention the variability in the difference between the sample means. (The light blue bands for each group are µ ± 2σ.)

Now select Actual data set from the pop-up menu.

To interpret what the difference between the sample means tells you about µ2  - µ1, you must understand its distribution.

Manipulative skills

To test the manipulative skill of job applicants, they are sometimes given a 'one-hole test' in which they grasp a pin, move it to a hole, insert it, and return for another pin. The test score is the number of pins inserted in a fixed time interval. A large study was undertaken comparing male college students with experienced female industrial workers. The table below describes the number of pins inserted in one minute.

Group n mean s
Male college students    750       35.12       4.31   
Experienced female industrial workers 412 37.32 3.83

The simulation uses these values as population parameters.

Welders who are paid a salary and those on piecework

This example is described in the diagram