Question

1. A sample of 35 circuits from a large normal population has
a mean resistance of 2.35 ohms. We know from past testing that
the

a) population standard deviation is 0.45 ohms. b) population
standard deviation is 0.48 ohms. c) population standard deviation
is 0.43 ohms. d) population standard deviation is 0.46 ohms.

Determine a 95% confidence interval for the true mean
resistance of the population

2. a)Arandomsampleofn=20has x=45ands=8.

b)Arandomsampleofn=22has x=48ands=9.

c)Arandomsampleofn=20has x=45ands=8.

d)Arandomsampleofn=22has x=48ands=9. Form a 95% confidence
interval for μ.

3. A random sample of 125 people shows that a) 30 are
left-handed.

b) 35 are left-handed. c) 40 are left-handed. d) 45 are
left-handed.

Form a 90% confidence interval for the true proportion of
left-handers

4. If = 45, what sample size is needed to estimate the mean
within a. ± 5 with 90% confidence?

b. ± 5 with 95% confidence? c. ± 4 with 90% confidence? d. ± 4
with 99% confidence?

5. How large a sample would be necessary to estimate the true
proportion of defectives in a large population within ±5%, with 99%
confidence?

a) Assume a pilot sample yields p = 0.16 b) Assume a pilot
sample yields p = 0.19 c) Assume a pilot sample yields p = 0.21 d)
Assume a pilot sample yields p = 0.23

Answer #1

( 1 )

( a )

**95 % c.i 2.201 <
< 2.499**

**95 % c.i** 2.20 < **
< 2.50 ( two decimals )**

**( b )**

population standard deviation is 0.48 ohms

**95 % c.i** 2.191<
< 2.509

95 % c.i 2.19 < **
< 2.51 ( two decimals )**

( c )

population standard deviation is 0.43 ohms.

**95 % c.i 2.208** <
< 2.492

95 % c.i 2.21 < **
< 2.49 ( two decimals )**

( d )

population standard deviation is 0.46 ohms

95% c.i 2.198 < < 2.502

95% c.i 2.20 < **
< 2.50 ( two decimals )**

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