Question 471101: Please, please help! i am stuck on my statistics homework and could use the help to see and know how this is done for future assignments.
here is the assignment:
Resource: Statistics for Psychology
Prepare a written response to the following assignments located in the text:
• Ch. 1, Practice Problems: 12, 15, 19, 20, 21, and 22.
Note. Methods of computation may include the usage of Excel, SPSS™, Lotus®, SAS®, Minitab®, or by-hand computation.
here is one of the questions:
15. Following are the speeds of 40 cars clocked by radar on a particular road in a
35-mph zone on a particular afternoon:
30, 36, 42, 36, 30, 52, 36, 34, 36, 33, 30, 32, 35, 32, 37, 34, 36, 31, 35, 20,
24, 46, 23, 31, 32, 45, 34, 37, 28, 40, 34, 38, 40, 52, 31, 33, 15, 27, 36, 40
Make (a) a frequency table and (b) a histogram. Then (c) describe the general
shape of the distribution.
thank you so much in advance!
bridget
Answer by Edwin McCravy(20060)   (Show Source):
You can put this solution on YOUR website!
The largest value is 52
The smallest value is 15
We will make 6 classes:
To determine the class width
1. Subtract 52-15 = 37
2. Divide by 6. 37÷6 = 6.166666667
3. Round to 6
The smallest class begins at the smallest number
1st class goes from 15 to 15+6 = 21
2nd class goes from 22 to 22+6 = 28
3rd class goes from 29 to 29+6 = 35
4th class goes from 36 to 36+6 = 42
5th class goes from 43 to 43+6 = 49
6th class goes from 50 to 50+6 = 56
Classes frequencies
15 - 21 2
22 - 28 4
29 - 35 17
36 - 42 13
43 - 49 2
50 - 56 2
----------------------
Total 40
------------------------------------
Make the histogram, starting and ending
the bars halfway between the class bounds.
I put the frequencies on top of the bars.
(Your teacher may vary from this, as there
is no standard way to do this. Some people
put a vertical frequency axis.)
To determine if it is bell-shaped, we calculate the
mean as 34.325 and the standard deviation as 7.325
1 standard deviation below the mean is 34.325 - 7.325 = 27
1 standard deviation above the mean is 34.325 + 7.325 = 41.65
There are 21 values between those values, 21/40 = .775 = 77.5%
That is within 10% of 68%, so that fits the first part of the
criteria for being bell-shaped:
2 standard deviation below the mean is 34.325 - 2×7.325 = 19.6
1 standard deviation above the mean is 34.325 + 2×7.325 = 48.9
There are 37 values between those values, 37/40 = .925 = 92.5%
That is within 5% of 95%, so that fits the second part of the
criteria of being bell-shaped.
So it is approximately bell-shaped.
Edwin
|
|
|
