Some students wanted to determine the reaction time of a sample of people aged from 5–80 years. The students found three different methods of testing reaction time, as described in Fig. 1.1. Method 1: Ruler test • The subject rests their elbow on a table so that their wrist extends over the side. • The assessor holds the ruler vertically in the air between the thumb and first finger of the subject. • The zero mark on the ruler is lined up with the first finger of the subject. The ruler is released without warning. • As soon as the subject sees the ruler fall, they catch it as quickly as possible. • The distance the ruler falls is recorded in metres. Method 2: Computer click timer • The subject looks at a computer screen and clicks a start button on the screen and waits for the background colour to change. • As soon as the background colour changes the subject clicks a stop button on the screen. • The reaction time, in seconds, appears on the screen. Method 3: Light board test • The subject stands in front of a board with buttons arranged in a pattern. The buttons light up randomly. • As soon as a button lights up the subject presses the button to turn it off. • As soon as a button is pressed another button lights up. • The number of lights turned off in a set time is recorded. [Figure 1.1]

1. (a)(i)The students decided that Method 2 was the most suitable to use for testing subjects aged from 5–80 years. Suggest two reasons why Method 2 is the most suitable.[2]
2. (a)(ii)State the independent variable and the dependent variable in Method 2. independent variable dependent variable[2]
3. (a)(iii)Describe how the students could investigate the reaction time of a sample of people aged from 5–80 years, using Method 2. Your description should be set out in a logical order and be detailed enough to let another person follow it. Details of Method 2, as described on page 2, are not required.[6]
4. (b)(i)The students found some results on the internet for a reaction time test, as shown in Fig. 1.2. The error bars show ± 1 standard deviation (s). [Figure 1.2] The percentage change in mean reaction time for males between the ages of 5 years and 10 years is 47%. Calculate the percentage change in mean reaction time for females between the ages of 5 years and 10 years. Show your working and give your answer to the nearest whole number. .%[2]
5. (b)(ii)State two conclusions about the trends shown by the results in Fig. 1.2. 1 2[2]
6. (b)(iii)State a suitable statistical test that the students could use to find out if the difference in reaction times between males and females of the same age was significant. Give a reason for your answer. name of test reason[2]
7. (b)(iv)Suggest a null hypothesis for the test that you have chosen in (iii).[1]

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