SOLUTION: certain length measurement is performed 100 times The arithmetic mean reading is 10.85 m, and the standard deviation 0.01 m. How many readings fall within (a) +- 0.001 meters, (b

Algebra ->  Test -> SOLUTION: certain length measurement is performed 100 times The arithmetic mean reading is 10.85 m, and the standard deviation 0.01 m. How many readings fall within (a) +- 0.001 meters, (b      Log On


   



Question 1176482: certain length measurement is performed 100 times The arithmetic mean reading is 10.85 m, and the standard deviation 0.01 m.
How many readings fall within (a) +- 0.001 meters, (b) +- 0.01 meters, and (c) +- 0.1 meters from the mean value?

Also, calculate the tolerance limits for 90 and 95 percent confidence level.

Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
the number of measurements is 100.
the mean is 10.85 meters.
the standard deviation is .01 meters.

this is not a sample.
this is the population.

use the z-score formula to find the number of standard deviations from the mean.

the z-score formula is z = (x - m) / s

z is the z-score
x is the raw score
m is the raw mean
s is the standard deviation in this case bcause we are dealing with a population.


if the score is plus or minus .001 meters from the mean, then the low z-score and high z-score are calculated as follows.

low z-score = -.001 / .01 = -.1
high z-score = .001 / .01 = .1

the ratio of measurements between plus or minus .001 from the mean would therefore be equal to .0796557923.
the percent is equal to 100 times that = 7.97% rounded to 2 decimal places.

if the score is plus or minus .01 meters from the mean, then the low z-score and high z-score are calculated as follows.

low z-score = -.01 / .01 = -1
high z-score = .01 / .01 = 1

the ratio of measurements between plus or minus .01 from the mean would therefore be equal to .6826894809.
the percent is equal to 100 times that = 68.27% rounded to 2 decimal places.

if the score is plus or minus .1 meters from the mean, then the low z=score and high z-score are calculated as follows:

low z-score = -.1 /.01 = -10
high z-score = .1 / .01 = .10

the ratio of measurements between plus or minus .1 from the mean would therefore be equal to 1,
the percent is equal to 100 times that = 100%.

at two tailed confidence level of 90%, the low and high z-scores would be equal to plus or minus 1.645 rounded to 3 decimal places.

the low raw score is found by the following formula:
-1.645 = (x - 10.85) / .01
solve for x to get:
x = .01 * -1.645 + 10.85 = 10.83355

the high raw score is found by the following formula:
1.645 = (x - 10.85) / .01
solve for x to get:
x = .01 * 1.645 + 10.85 = 10.86645

at 95% confidence interval, the low and high z-scores would be equal to plus or minus 1.960 rounded to 3 decimal places = 1.96 rounded to 2 decimal places.

the low raw score is found by the following formula:
-1.96 = (x - 10.85) / .01
solve for x to get:
x = .01 * -1.96 + 10.85 = 10.8304

the high raw score is found by the following formula:
1.96 = (x - 10.85) / .01
solve for x to get:
x = .01 * 1.96 + 10.85 = 10.8696

visually, these look like as follows: