Transcript Sample Presentation

Sample Presentation
Research Question


Do students who own graphing
calculators study more than students
who do not?
Specifically, how do these two
groups compare on the average
number of hours spent studying in a
typical week?
Variables used
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
I used Q13: Do you own a graphing
calculator? to form two groups.
I used Q31: How many hours do you
study in a typical week? as a
quantitative variable.
Hours studied by students who
do own graphing calculators
Graphing calculator?: Yes
14
12
Frequency
10
8
6
4
2
Mean = 21.689
Std. Dev. = 14.0402
N = 45
0
0.0
10.0
20.0
30.0
40.0
50.0
hours on homework in a\ week
60.0
Students who own graphing
calculators
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

45 people in the sample own
graphing calculators
The average number of hours they
study in a typical week is 21.7 hours,
with a standard deviation of 14.0
hours.
The histogram is not symmetric: it
has a right hand tail.
Hours studied by students
without graphing calculators
Graphing calculator?: No
6
5
Frequency
4
3
2
1
Mean = 19.429
Std. Dev. = 8.6799
N = 14
0
0
10
20
30
40
50
hours on homework in a\ week
60
Students without graphing
calculators



14 people in the sample don’t own
graphing calculators.
On average they study 19.4 hours in a
typical week, with a standard deviation of
8.7 hours. (This is SD+)
The histogram is roughly symmetric,
although more people study 20-30 hours
than study 10 to 20 hours.
Hypothesis testing
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
Null hypothesis: there is no difference
between the average number of hours
studied in a typical week between
students with a graphing calculator and
students without.
Alternate hypothesis: Students who own a
graphing calculator spend more time on
homework.
Calculating SEavg
for each group
With graphing calculator:
SE avg = sqrt(45) x 14/45 = 2.1 hours

With no graphing calculator:
SE avg = sqrt(14) x 8.7/14 = 2.3 hours
SE for the difference
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The SE for the difference between
these two averages is
SEdiff = sqrt(2.32 + 2.12)
SEdiff = 3.1 hours
2-sample z-test
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
The difference between the two averages
is 21.7 – 19.4 = 2.3
The z-value for this difference is
2.3/SEdiff = 2.3/3.1 = 0.74
The area under the normal curve to the right
of z = 0.74 is approx
(100-54)/2 = 23%

P = 23% is much larger than 5%
Conclusion

We have to accept the null
hypothesis. There is no difference
between students with and those
without graphing calculators in the
average number of hours of study in
a typical week.