18. A set of data has a sample mean of 65.4 and a standard deviation of 1.2. If the sample size is 45, what is the 99% confidence interval of this data? A. 65.10 and 65.70
B. 65.33 and 65.47
C. 65.05 and 65.75
D. 64.94 and 65.86

Given:

Sample mean = 65.4

Standard deviation = 1.2

Sample size = 45

Confidence level = 99%

To find:

The confidence interval.

Solution:

The formula for confidence interval is

where, is sample mean, z* is confidence value, s is standard deviation and n is sample size.

Confidence value or z-value at 99% = 2.58

Putting the given in the above formula, we get

Therefore, the correct option is D.

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)