Due to a variation in laboratory techniques, impurities in materials, andotherun

Question

Due to a variation

in laboratory techniques, impurities in materials, andotherunknown factors, the results of an experiment ina chemistrylaboratory wilI not always yield the same

numerical answer. In an electrolysis expenment,a

class measured the amount of copper precipitatedfrom

a saturated solution of copper sulfate over a30-minute

period. The n = 30 students calculated a samplemean

and standard deviation equal to .145 and.0051 mole,

respectively. Find a 90% confidence interval for themean amountof copper precipitated from the solution

over a 30-minute period.

Explanation / Answer

n=30 mean, = 0.145 standard deviation, =0.0051 standard error, e = /n = 0.0051 / 30 for 90% confidence, z value = 1.65           (from z table) confidence interval, CI = ±ze = 0.145 ± 0.0015= (0.1435, 0.1465)

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