Let n = required random sample size.
Assume that the population standard deviation is known as σ.
Let m = sample mean.
At the 95% confidence level, the expected range is
(m - k(σ/√n), m + k(σ/√n))
where k = 1.96.
Therefore the error margin is 1.96(σ/√n).
Because the error margin is specified as 3% or 0.03, therefore
(1.96σ)/√n = 0.03
√n = (1.96σ)/0.03
n = 128.05σ²
This means that the sample size is about 128 times the population variance.
Answer:
Smallest sample size = 128.05σ², where σ = population standard deviation.
Answer:
yes it is right
Step-by-step explanation:
Let the distance be x miles
Time = Distance / speed
Time taken by Mike to go to his friend's house = x / 40 hours
Time taken by him to return = x / 45 hours
Total time = x / 40 + x / 45 = 4 hours
= 9x + 8x = 1440 miles
17x = 1440
= x = 1440 ÷ 7
= x = 84.706
Time taken to return home = 84.706 /45= 1.882 hours .
Therefore , Mike took 1.882 hours to reach home .
Answer:
Step-by-step explanation:
