In descriptive statistics, what does the "confidence level" mean?

D

Dora Smith

Here are teh descriptive statistics for one of my columns.

Total Records Collected

Mean 617,416.82
Standard Error 38,027.85
Median 629,507.50
Mode #N/A
Standard Deviation 201,224.45
Sample Variance 40,491,281,082.30
Kurtosis -0.26
Skewness 0.21
Range 829,194.00
Minimum 248,690.00
Maximum 1,077,884.00
Sum 17,287,671.00
Count 28.00
Confidence Level(95.0%) 78,026.70



I thought it would be great to get the confidence interval, but instead it
gives me a "confidence level" that doesn't even make sense, and the manual
does not discuss what the "confidence level" is. Frankly the number is
far too small in relation to the mean and the standard deviation to appear
to make sense.

I want to know the level one can have 95% confidence of achieving. That's
the only confidence level that has any meaning to me. That figure would
have to be a couple of standard deviations above 617,000, it seems to me.
Not, 78,026. Since the SD is 201,000, what does the number 78,026 even
mean?

What exactly is Excel's "confidence level"?
 
J

Jerry W. Lewis

If you are willing to assume that the data came from a normal distribution
with unknown mean and standard deviation, then a 95% confidence interval for
the mean is
617,416.82 +/- 78,026.70
which is the interval
539390.12 to 695443.52

Jerry
 

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