Practice Makes Perfect Statistics In Your World 
Student Notes
Teachers Notes
Catching a Ruler
 
Results (non-writing hand)
 
Results (writing hand)
 
Plotting Both Reaction Times
 
Mean Times
 

Reaction Times

Catching a Ruler
You will need:
Page R1, some sellotape and a 30 cm ruler.

Work with a partner.

a Cut out Figure 7 from page Rl and tape it to your ruler.

Your teacher will explain in detail what you have to do. Your partner will hold the ruler just above your hand. As soon as he lets go, you have to catch it between your finger and thumb. The markings on the ruler tell you how long it took you to react.

b Practice ONCIE ONLY with each hand.

When you have had this one practice, drop the ruler once more through each hand.

c Find the reaction time with your non-writing hand. Write it down.
d Find the reaction time with your writing hand. Write it down.
e Give your results to your teacher.
f Complete Tables 1 and 2 on page Rl.

 

Class Results (non-writing hand)
You will need Table 1 and squared paper.

a Write down the slowest reaction time.
b Write down the quickest reaction time.
c Subtract the quickest reaction time from the slowest reaction time.

This is the RANGE ot'the class reaction times using the non-writing hand.

The children in Class 2c at Parkville School did the same experiment. Their results are shown as a bar chart in Figure 1.


Figure 1 - Reaction times (non- writing hand), Parkville School.

d Draw a bar chart to show your class results from Table 1.

At Parkville the most common reaction time (the one with the tallest bar) is 18 hundredths of a second. We say that the MODE is 18/100 seconds.

e Write down the mode for your class results.

 

Class Results (writing hand)
You will need Table 2 and squared paper.

a Draw a bar chart to show your class results with the writing hand (Table 2).
b Write down the mode.
c Write down the slowest reaction time.
d Write down the fastest reaction time.
e Write down the range of the reaction times.

Compare the results of the writing hand with those of the non-writing hand.

f Which hand had the higher mode (slower reaction time)?
g Which hand had the greater range (more variation)?

 

Plotting Both Reaction Times
You will need a sheet of squared paper.

Figure 2 shows the results of two pupils. The reaction time with the writing hand is on the horizontal scale, with the other hand on the vertical scale. The point (+) on the left is of a boy whose reaction times were 10 hundredths of a second with the writing hand and 12 hundredths of a second with the other hand. The point (O) on the right shows the results of a girl with a reaction time for the writing hand of 13 hundredths of a second and 11 hundredths of a second with the other hand.

a Make a diagram like this which has a point for each pupil in your class.


Figure 2 - Reaction times for our class.

This sort of diagram is called a SCATTERGRAM.

b Can you see any patterns?
c What does your scattergram suggest about reaction times?

*Mean Times
You will need Tables 1 and 2.

a Add up the reaction times with the writing hand of all the pupils in your class.
b Divide this by the number of pupils in the class. You now have the mean reaction time with the writing hand.
c Find the mean reaction time with the non-writing hand.
d Which hand gave the larger mean?
e Was this what you expected?
f Why?

 

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