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Confidence Intervals Can someone check my work to see if done this correctly. As you can see i made up 36 gas prices and my formula answers are in...
Confidence Intervals
Can someone check my work to see if done this correctly. As you can see i made up 36 gas prices and my formula answers are in bold. I want to know if i done this correctly and i would love to learn your input on this. I followed the example it told me to do which is down below. Thank you for checking my confidence intervals.
$1.65 $1.78 $1.88 $1.89 $1.99 $2.00 $2.02 $2.04 $2.21 $2.22 $2.23 $2.27 $2.31 $2.34 $2.42 $2.43 $2.44 $2.50 $2.51 $2.52 $2.53 $2.55 $2.56 $2.57 $2.58 $2.71 $2.75 $2.85 $2.87 $2.89 $2.99 $3.02 $3.09 $3.12 $3.11 $2.24
I used Excel formulas:
Mean - AVERAGE(A2:A37) =2.45
Standard deviation - STDEV(A2:A37) = 0.393
Confidence Norm - CONFIDENCE.NORM(0.5,0.39,36) = 0.043
Confidence Interval - (2.05, 2.49)
Example below:
- First find the mean. List all 36 gas prices in cells A1 to A36 in your excel spreadsheet.
- On a different cell type in =average(A1:A36) and the hit enter to find the average
- Assume your answer is 2.65
- On a different cell type in =stdev.s(A1:A36) or =stdevA(A1:A36) and enter to find the standard deviation
- Assume your answer is .43
- Then put this in an excel cell =confidence.norm(.05,.43,36) and hit enter. This is the E value
- So take the mean of 2.65 and you have (2.65-E, 2.65+E) for your confidence interval
