In a standard normal distribution, what percentage of observations lie between [tex]$z = 0.37$[/tex] and [tex]$z = 1.65$[/tex]?

A. 30.62%
B. 40.52%
C. 50.48%
D. 69.30%



Answer :

To find the percentage of observations that lie between [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex] in a standard normal distribution, we follow these steps:

1. Find the Cumulative Distribution Function (CDF) value for [tex]\( z = 0.37 \)[/tex]:
- The CDF value for [tex]\( z = 0.37 \)[/tex] is [tex]\( 0.6443 \)[/tex]. This means that approximately 64.43% of the observations in a standard normal distribution are less than [tex]\( z = 0.37 \)[/tex].

2. Find the Cumulative Distribution Function (CDF) value for [tex]\( z = 1.65 \)[/tex]:
- The CDF value for [tex]\( z = 1.65 \)[/tex] is [tex]\( 0.9505 \)[/tex]. This means that approximately 95.05% of the observations in a standard normal distribution are less than [tex]\( z = 1.65 \)[/tex].

3. Calculate the percentage of observations between [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex]:
- To find the percentage of observations that lie between [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex], we subtract the CDF value for [tex]\( z = 0.37 \)[/tex] from the CDF value for [tex]\( z = 1.65 \)[/tex]:
[tex]\[ 0.9505 - 0.6443 = 0.3062 \][/tex]

4. Convert the result to a percentage:
- To express the result as a percentage, we multiply by 100:
[tex]\[ 0.3062 \times 100 = 30.62\% \][/tex]

Thus, approximately 30.62% of the observations lie between [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex].

Among the provided options, the correct answer is [tex]\( \boxed{30.62\%} \)[/tex].