# Reaction time

This activity is an example of a semi-structured statistical investigation.

Set the question:
Which group is quickest at grabbing a ruler?

### Data collection

Hold a ruler near the end (highest number) and let it hang down. Have another person put his or her hand at the bottom of the ruler without touching it and ask that person ready to be ready grab the ruler. Tell the person that you will drop the ruler sometime within the next 5 seconds and that he or she is supposed to catch the ruler as quickly as possible after it is dropped. Record the measure on the ruler at the point the ruler is caught.

### Representing data

Record the ruler measurements in a table for each person in the class, with the data for other attributes such as gender, age or eye colour.

Use stacked dot plots to compare the data collected from two different classes, different year groups, girls and boys, or brown-eyed people and people with other eye colours.

### Summarising data

Discuss the characteristics of stacked dot plots that may help students to draw conclusions about the data when comparing groups.

### Degree of certainty

Discuss the features of the graphs that may add to studentsâ€™ confidence the groups are the same or different, or make them uncertain there is a difference between the groups.

### Drawing a conclusion

Make a statement about which group is quickest at grabbing the ruler including the way the graphs contribute to the certainty about the conclusion drawn.