Required practical activity 7: Plan and carry out an investigation into the effect of a factor on human reaction time

Question 1

Reaction time:

Answer 1

the time it takes you to respond to a stimulus

Question 2

What is caffeine?

Answer 2

a drug that can speed up a person’s reaction time

Question 3

Method for measuring the effect of a factor on human reaction time:

Answer 3

(Need to talk about sample size, calculating a mean & increasing accuracy)

1. Person being tested should sit with their arm resting on edge of table - prevents them from moving their arms up and down during test
2. Hold ruler vertically between their thumb and forefinger - ensure zero end of ruler is level with their thumb and finger - then let go of ruler without giving any warning
3. The person should try to catch the ruler as quickly as they can - as soon as they see it fall
4. Reaction time is measured by the number on the rules where it’s caught - top of the thumb (further down the rules it is caught the slower the reaction time)
5. Repeat several times then calculate mean distance that the ruler fell
6. Person being tested should have caffeinated drink - after 10mins repeat steps 1 to 5 to allow time for caffeine to take effect
7. Control any variables to ensure its a fair test (use same person to catch rules each time, should use same hand and make sure that they haven’t had any caffeine before start of experiment
8. Too much caffeine can cause unpleasant side effects so person being test should avoid drinking caffeine for rest of day after experiment is completed
9. Control more variables e.g. the hand the person uses to catch ruler to increase validity (always use dominant hand)
10. Increase sample size - make sure everyone uses dominant hand

Question 4

Formula to calculate reaction time:

Answer 4

t = √(2d / a)

t = time in seconds

d = distance in metres

a = acceleration as a result of gravity = 9.81m/s²

Question 5

Improvements to increase validity:

Answer 5

• more repeats
• test more students
• use ruler with more precise scale – e.g. mm scale
• drop the ruler from same height (above the hand)
• make sure student B’s hand is stationary - keep arm resting on edge of table
• use same type/weight of ruler
• drop ruler without any force each time
• use same/dominant hand each time
• same distance between finger(s) and thumb
• thumb same distance from ruler at the start