Answer: C.-1.5
Step-by-step explanation:
Given: The burning time of a very large candle is normally distributed with mean of 2500 hours and standard deviation
of 20 hours.
Let X be a random variable that represent the burning time of a very large candle.
Formula:
For X = 2470
So, the z-score they corresponds to a lifespan of 2470 hours. =-1.5
Hence, the correct option is C.-1.5.
Answer:
a)0.6192
b)0.7422
c)0.8904
d)at least 151 sample is needed for 95% probability that sample mean falls within 8$ of the population mean.
Step-by-step explanation:
Let z(p) be the z-statistic of the probability that the mean price for a sample is within the margin of error. Then
z(p)= where
a.
z(p)= ≈ 0.8764
by looking z-table corresponding p value is 1-0.3808=0.6192
b.
z(p)= ≈ 1.1314
by looking z-table corresponding p value is 1-0.2578=0.7422
c.
z(p)= ≈ 1.6
by looking z-table corresponding p value is 1-0.1096=0.8904
d.
Minimum required sample size for 0.95 probability is
N≥ where
then N≥ ≈150.6
Thus at least 151 sample is needed for 95% probability that sample mean falls within 8$ of the population mean.