[Review Candy Questions for Exam 1]
19a
. Given
: You take 20 length measurements of a strut. You calculate
x
= 8.28 cm and
S
=
0.43 cm. The true value is 8.26 cm.
To do
: Calculate the systematic error.
Solution
:
19b
. Given
: You take 20 length measurements of a strut. You calculate
x
= 8.28 cm and
S
=
0.43 cm. The true value is 8.26 cm.
To do
: Calculate the 95% confidence interval for the population mean. In other words, we
would estimate the population mean as
μ
= 8.28 +/ ___________ cm.
Solution
:
20
. Given
: A company produces parts for motorcycles by the thousands, and Jonathan is in
charge of quality control.
•
He picks 30 parts at random as sample 1, and calculates the mean,
1
x
.
•
He picks 30
other
parts as sample 2, and calculates the mean,
2
x
.
•
…
•
Jonathan continues to do this until sample 20, and calculates the mean,
20
x
.
The
average
of all the means is
( )
11
2
2
0
...
/20 13.55 mm
xx
x
x
=+
+
+
=
.
The
sample
standard deviation
of all the means is
0.22 mm
x
S
=
.
To do
: Estimate the
population standard deviation,
σ
.
Give your answer in mm to three
significant digits.
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 Spring '08
 staff
 Statistics, Standard Deviation, Mean, Null hypothesis

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