The question is incomplete! Complete question along with answer and step by step explanation is provided below.
Question:
The lifetime (in hours) of a 60-watt light bulb is a random variable that has a Normal distribution with σ = 30 hours. A random sample of 25 bulbs put on test produced a sample mean lifetime of = 1038 hours.
If in the study of the lifetime of 60-watt light bulbs it was desired to have a margin of error no larger than 6 hours with 99% confidence, how many randomly selected 60-watt light bulbs should be tested to achieve this result?
Given Information:
standard deviation = σ = 30 hours
confidence level = 99%
Margin of error = 6 hours
Required Information:
sample size = n = ?
Answer:
sample size = n ≈ 165
Step-by-step explanation:
We know that margin of error is given by
Margin of error = z*(σ/√n)
Where z is the corresponding confidence level score, σ is the standard deviation and n is the sample size
√n = z*σ/Margin of error
squaring both sides
n = (z*σ/Margin of error)²
For 99% confidence level the z-score is 2.576
n = (2.576*30/6)²
n = 164.73
since number of bulbs cannot be in fraction so rounding off yields
n ≈ 165
Therefore, a sample size of 165 bulbs is needed to ensure a margin of error not greater than 6 hours.
Answer:
<u>CIRCLE : CIRCLE</u>
Ratio of area is the scale factor squared. So find the radii of the two circles, square both values, and simplify the ratio.
<u>SQUARE : SQUARE</u>
Ratio of area is the scale factor squared, So find the side lengths of the two squares, square both values, and simplify the ratio.
<u>SQUARE : CIRCLE</u>
Using the formulas A = s*s and A = pi*r^2, find the areas of the circle and the square. Then simplify the ratio.
Answer:
y = -2x - 2
Step-by-step explanation:
Slope-Intercept Form: y = mx + b
Points: (3, 4)
Slope: -2
y = -2x + b
4 = -2 ( 3 ) + b
4 = -6 + b
b = -2
y = -2x - 2
Answer:
20%
Step-by-step explanation:
1/5 of 1 hour = 20 minutes
so 1/5 = 20%
25% + 20% = 45%
0.35 = 35%
45% + 35% = 80%
100% - 80% = 20%
Answer = 20%
Hope this helps!
