Group:______

Names:

Is your dominant hand stronger than your other hand? Right-handed individuals use their right hands for many more activities than their left, and lefties use their left hands more often. Does all of this extra use mean that their dominant hands are stronger? In this study we will examine the differences in the strength of the right and left hands of a group of volunteers from your class using a device called a hand dynamometer. This device measures the strength (in Newtons of force) of a person’s grip and sends it to a calculator.

Designing our study:

Before we begin we need to develop a procedure to collect our measurements. Take a few minutes to discuss as a class the procedure to be used. Some questions to consider will be:

  • Do you measure the grip at the moment when they first start squeezing or after a few seconds (the grip will become weaker as time goes of)?
  • Which hand will be used first? Dominant or off-dominant?
  • What position will the subject be in for the measurement (standing, sitting, arms outstretched, by their sides, etc.)?

Write a brief description of how the measurements will be taken based on the whole class discussion.

What will the data look like?

We will be taking two measurements of the strength of each person, but what we really care about is the difference in these two measures. We will subtract the off-dominant hand measure from the dominant measure.

If there is no difference?

If there is no difference in the hand strength then each individual should have a difference that is around ______.

If the dominant hand is stronger?

If the dominant hand is stronger we would expect the differences in our measures to be ______zero.

a.greater than

b.less than

c.about

Null Hypothesis:

Hypothesis tests begin by assuming that there is no effect and then looking for evidence of an effect. For this scenario we will begin by assuming for our null hypothesis that there is no difference for the right and left hands. Consider your answers to the previous questions. If there is no difference in the strength of the hands we would have a null hypothesis that is:

H0: ______

Alternative Hypothesis:

Based on the fact that the dominant hand gets more exercise than the off-dominant hand we would expect that the dominant hand is stronger than the off-dominant. What alternative hypothesis would represent the dominant hand being stronger than the off-dominant?

Ha: ______

The Data:

Record the measures from the 10 volunteers here:

Subject / Dominant / Off-dominant / Difference
1
2
3
4
5
6
7
8
9
10

Summary statistics:

For the column of differences calculate the following:

  • The mean ():______
  • The standard deviation: ______
  • The sample size:_____

The test statistic:

Recalling your null hypothesis calculate a standard score for your sample mean (using the sample standard deviation).

Test statistic:______

The p-value:

Recall that since we are using the sample standard deviation this statistic should have a t-distribution. Based on our sample size what is the appropriate number of degrees of freedom?

Degrees of freedom: ______

Find the appropriate p-value for this test statistic. Remember to use the alternative hypotheses you specified above.

p-value:_____

The conclusion:

Based on the p-value you calculated above what conclusion would we make about the null hypothesis?

  1. Reject H0.
  2. Fail to reject H0.

Based on your conclusion about the null hypothesis what conclusion do you make about the strength of the dominant and off-dominant hand?

Page 1 of 3