Answer:
a) Mean = 382.3 psi
Standard deviation = 20.8 psi
b) 392.7 psi
c) P(X<400)=0.8026
Step-by-step explanation:
a) The population mean can be estimated as equal to the mean of the sample, and the population standard deviation can be estimated from the sample standard deviation:


b) We start by searching for the z-value for the 95th percentile. This value is
z=1.645:

Then, the strength value below which 95% of all welds will have their strengths is:

c) We calculate the probability of X being equal or less than 400 as:

Answer:
ok that is correct because you start with 25 and then add 9 each week so 25+9w
Step-by-step explanation:
Answer:
C and D
Step-by-step explanation:
(X-3)(X+7)=0
X-3=0 X+7=0
X=3 X=-7
Answer: A:it consists of the entire population.