- #1
ldlafountain
- 3
- 0
I am working on a problem for my Statistics class and I am looking for some clarification and some direction.
The questions asks about a study that has been done on the diameter of 50 screws (both digital and vernier scale calipers). The differences in the measured diameters had the following frequency distribution.
Difference: Frequency:
-0.03 1
-0.02 3
-0.01 11
0.00 19
0.01 10
0.02 6
I am then asked to make a 90% two sided interval for the mean difference in digital and vernier readings.
So naturally I find the mean of all of the differences by adding up all the differences (by their frequencies) and I get 0.004 as my mean and 0.1148 as my standard deviation. Next I would try and find the t-value for Q(.95) (because we are using a 90% two sided confidence interval). I had to look it up online I came up with 1.677. I would plug this all into the following equation:
x-bar (plus-minus) t*(s/sqrt(n))
I have tried this multiple times and I keep obtaining the wrong intervals. According to the back of my book I should obtain the answer [-0.0023,0.0031], but I come nowhere near. Can anyone help me? If there is something wrong with my math or the way I set up the problem, please let me know. I am thankful for any help.
The questions asks about a study that has been done on the diameter of 50 screws (both digital and vernier scale calipers). The differences in the measured diameters had the following frequency distribution.
Difference: Frequency:
-0.03 1
-0.02 3
-0.01 11
0.00 19
0.01 10
0.02 6
I am then asked to make a 90% two sided interval for the mean difference in digital and vernier readings.
So naturally I find the mean of all of the differences by adding up all the differences (by their frequencies) and I get 0.004 as my mean and 0.1148 as my standard deviation. Next I would try and find the t-value for Q(.95) (because we are using a 90% two sided confidence interval). I had to look it up online I came up with 1.677. I would plug this all into the following equation:
x-bar (plus-minus) t*(s/sqrt(n))
I have tried this multiple times and I keep obtaining the wrong intervals. According to the back of my book I should obtain the answer [-0.0023,0.0031], but I come nowhere near. Can anyone help me? If there is something wrong with my math or the way I set up the problem, please let me know. I am thankful for any help.