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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:
o 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)?
o Which hand will be used first? Dominant or off-dominant?
o 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 _______.
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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 offdominant?
Ha: _________
The Data:
Record the measures from the 10 volunteers here:
Subject
1
2
3
4
5
6
7
8
9
10
Dominant
Off-dominant
Summary statistics:
For the column of differences calculate the following:
o The mean ( x ):________
o The standard deviation: ______
o The sample size:_____
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Difference
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 tdistribution. 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?
a. Reject H0.
b. 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?
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