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Sagot :
Answer:
90% Confidence Interval for the total cash value = ($1,145.49, $2,982.51)
Step-by-step explanation:
(a) Margin of Error and Confidence Interval
Given Data:
Sample mean (
ˉ
x
ˉ
) = $6.88 per 100 pounds
Sample standard deviation (
σ) = $1.86 per 100 pounds
Sample size (
n) = 37
Confidence level = 90%
Steps:
Find the Z-score for a 90% confidence level:
For a 90% confidence level, the Z-score is approximately 1.645. This value is obtained from the standard normal distribution table for a 90% confidence interval (which leaves 5% in each tail).
Calculate the margin of error (ME):
The margin of error formula is:
=
×
ME=Z×
n
σ
Plugging in the values:
=
1.645
×
1.86
37
ME=1.645×
37
1.86
≈
1.645
×
1.86
6.08
ME≈1.645×
6.08
1.86
≈
1.645
×
0.306
ME≈1.645×0.306
≈
0.504
ME≈0.504
Margin of Error (ME) ≈ $0.50
Find the 90% confidence interval:
The confidence interval is given by:
ˉ
±
x
ˉ
±ME
6.88
±
0.50
6.88±0.50
Confidence Interval
=
(
6.38
,
7.38
)
Confidence Interval=(6.38,7.38)
90% Confidence Interval = ($6.38, $7.38)
(b) Sample Size for a 90% Confidence Level
Given Data:
Desired margin of error (
E) = $0.27
Sample standard deviation (
σ) = $1.86
Confidence level = 90%
Steps:
Find the Z-score for a 90% confidence level:
The Z-score is 1.645.
Calculate the required sample size (
n):
The formula for sample size is:
=
(
×
)
2
n=(
E
Z×σ
)
2
Plugging in the values:
=
(
1.645
×
1.86
0.27
)
2
n=(
0.27
1.645×1.86
)
2
=
(
3.0587
0.27
)
2
n=(
0.27
3.0587
)
2
=
(
11.32
)
2
n=(11.32)
2
≈
128.1
n≈128.1
Sample Size
n ≈ 129 (rounding up to ensure sufficient accuracy)
(c) Margin of Error and Confidence Interval for Cash Value
Given Data:
Farm brings 15 tons of watermelon.
1 ton = 2,000 pounds, so 15 tons = 30,000 pounds.
Price per 100 pounds = $6.88
Standard deviation = $1.86 per 100 pounds
Confidence level = 90%
Steps:
Calculate the total cash value of the crop:
Total cash value:
Value
=
30
,
000
100
×
6.88
Value=
100
30,000
×6.88
Value
=
300
×
6.88
Value=300×6.88
Value
=
2
,
064
Value=2,064
Find the margin of error for the total value:
First, find the standard deviation for the total value. Since the price per 100 pounds is given:
Standard deviation for total value
=
30
,
000
100
×
Standard deviation for total value=
100
30,000
×σ
Standard deviation for total value
=
300
×
1.86
Standard deviation for total value=300×1.86
Standard deviation for total value
=
558
Standard deviation for total value=558
Now calculate the margin of error for the total cash value:
=
×
Standard deviation for total value
ME=Z×Standard deviation for total value
=
1.645
×
558
ME=1.645×558
≈
918.51
ME≈918.51
Margin of Error ≈ $918.51
Find the 90% confidence interval for the total cash value:
The confidence interval is given by:
Value
±
Value±ME
2
,
064
±
918.51
2,064±918.51
Confidence Interval
=
(
1
,
145.49
,
2
,
982.51
)
Confidence Interval=(1,145.49,2,982.51)
90% Confidence Interval for the total cash value = ($1,145.49, $2,982.51)
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