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

A. [tex]$30.62\%$[/tex]
B. [tex]$40.52\%$[/tex]
C. [tex]$59.48\%$[/tex]
D. [tex]$69.38\%$[/tex]



Answer :

Alright, let's go through the process of solving this question step-by-step.

### Understanding the Problem
We are given two z-scores, [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex], and we need to find the percentage of observations that lie between these two z-scores in a standard normal distribution.

### Standard Normal Distribution
A standard normal distribution is a normal distribution with a mean of 0 and a standard deviation of 1. The z-score represents the number of standard deviations a point is from the mean.

### Z-Scores and Cumulative Distribution Function (CDF)
The cumulative distribution function (CDF) for a z-score gives us the probability that a standard normal random variable will be less than or equal to that z-score.

### Finding Probabilities
1. For [tex]\( z = 0.37 \)[/tex]:
The CDF value (probability) corresponding to [tex]\( z = 0.37 \)[/tex] is approximately 0.6443 (or 64.43%).

2. For [tex]\( z = 1.65 \)[/tex]:
The CDF value (probability) corresponding to [tex]\( z = 1.65 \)[/tex] is approximately 0.9505 (or 95.05%).

### Calculating the Percentage Between the Two Z-Scores
The percentage of observations that lie between [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex] is found by subtracting the probability at [tex]\( z = 0.37 \)[/tex] from the probability at [tex]\( z = 1.65 \)[/tex] and then converting this probability to a percentage.

1. Subtracting the Probabilities:
[tex]\( 0.9505 - 0.6443 = 0.3062 \)[/tex]

2. Converting to Percentage:
[tex]\( 0.3062 \times 100 = 30.62\% \)[/tex]

### Conclusion
Therefore, the percentage of observations that lie between [tex]\( z = 0.37 \)[/tex] and [tex]\( z = 1.65 \)[/tex] in a standard normal distribution is [tex]\( 30.62\% \)[/tex].

Given the options provided:

[tex]\( 30.62 \% \)[/tex]

[tex]\( 40.52 \% \)[/tex]

[tex]\( 59.48 \% \)[/tex]

[tex]\( 69.38 \% \)[/tex]

The correct answer is:

[tex]\[ \boxed{30.62\%} \][/tex]

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