Question

-0.07 0.07 z 2. A bank has kept records of the checking balances of its customers and determined that the average daily balance of its customers is $300 with a standard deviation of $48, and is a normally distributed population. A random sample of 144 checking accounts is selected a) What is the probability that the sample mean will be at least $306.60? b) What is the probability that the sample mean will be less than $308?

Answer 1

meau ll = 300 SD 248 nz 144 meau Mx el=300 meau of the sample standard devation the sample mean t = 1 48 1744 4. the (ма. is atleast 306.60 a probability that sample PCãy 306.60) = P( a-MT 306.60 – 300) Tx 4 -P (7 7 1.65) 10.0995 u 306.6 X-4x L308-300 4 Tx 4= 307 308 & probability that the sample mean will be less than 308 es P( x < 308) = PC =P(222) 0.9772 probability that the sample mean is between 302 and 308 u PC 302 c# <308) 302-300 x 4ă =P(0.52 Z22) =PL 4. 1308-300 4 Tă 0.2857 M=30802 308