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Raw scores on a certain standardized test one year were normally distributed, with a mean of 156 and a standard deviation of 23. If 48,592 students took the test, about how many of the students scored less than 96?

\begin{tabular}{|c|c|c|c|c|c|c|c|c|}
\hline \multicolumn{8}{|c|}{ Table shows values to the LEFT of the [tex]$z$[/tex]-score } \\
\hline [tex]$z$[/tex] & 0.00 & 0.01 & 0.02 & 0.03 & 0.04 & 0.05 & 0.06 & 0.07 \\
\hline 2.5 & 0.99379 & 0.99396 & 0.99413 & 0.99430 & 0.99446 & 0.99461 & 0.99477 & 0.99492 \\
\hline 2.6 & 0.99534 & 0.99547 & 0.99560 & 0.99573 & 0.99585 & 0.99598 & 0.99609 & 0.99621 \\
\hline 2.7 & 0.99653 & 0.99664 & 0.99674 & 0.99683 & 0.99693 & 0.99702 & 0.99711 & 0.99720 \\
\hline 2.8 & 0.99744 & 0.99752 & 0.99760 & 0.99767 & 0.99774 & 0.99781 & 0.99788 & 0.99795 \\
\hline 2.9 & 0.99813 & 0.99819 & 0.99825 & 0.99831 & 0.99836 & 0.99841 & 0.99846 & 0.99851 \\
\hline -2.9 & 0.00187 & 0.00181 & 0.00175 & 0.00169 & 0.00164 & 0.00159 & 0.00154 & 0.00149 \\
\hline -2.8 & 0.00256 & 0.00248 & 0.00240 & 0.00233 & 0.00226 & 0.00219 & 0.00212 & 0.00205 \\
\hline -2.7 & 0.00347 & 0.00336 & 0.00326 & 0.00317 & 0.00307 & 0.00298 & 0.00289 & 0.00280 \\
\hline -2.6 & 0.00466 & 0.00453 & 0.00440 & 0.00427 & 0.00415 & 0.00402 & 0.00391 & 0.00379 \\
\hline -2.5 & 0.00621 & 0.00604 & 0.00587 & 0.00570 & 0.00554 & 0.00539 & 0.00523 & 0.00508 \\
\hline
\end{tabular}

A. 18,627
B. 60
C. 220
D. 19,312


Sagot :

To determine how many of the 48,592 students scored less than 96 on the standardized test, we need to follow these steps:

1. Find the z-score:
The z-score tells us how many standard deviations a particular score is from the mean. The formula to calculate the z-score is:
[tex]\[ z = \frac{X - \mu}{\sigma} \][/tex]
where:
- [tex]\( X \)[/tex] is the score of interest (96 in this case).
- [tex]\( \mu \)[/tex] is the mean (156).
- [tex]\( \sigma \)[/tex] is the standard deviation (23).

Plugging in the given values:
[tex]\[ z = \frac{96 - 156}{23} = \frac{-60}{23} \approx -2.6087 \][/tex]

2. Look up the cumulative probability for the z-score [tex]\( -2.6087 \)[/tex]:
We need to look up the cumulative probability from the z-table, which tells us the probability that a score is less than a given z-score. Checking the z-table for [tex]\( z \approx -2.61 \)[/tex] (rounding [tex]\( -2.6087 \)[/tex] to [tex]\( -2.61 \)[/tex]), we get a cumulative probability approximately [tex]\( 0.00454 \)[/tex].

3. Calculate the number of students below the given score:
To find the number of students who scored less than 96:
[tex]\[ \text{Number of students} = \text{cumulative probability} \times \text{total number of students} \][/tex]
Plugging in the values:
[tex]\[ \text{Number of students} = 0.00454 \times 48592 \approx 220.82 \][/tex]

Since the number of students must be a whole number, we approximate to the nearest whole number. Thus, about 221 students scored less than 96.

Therefore, the number of students who scored less than 96 is approximately:
[tex]\[ \boxed{220} \][/tex]
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