Respuesta :
Answer:
a. Above 337.8 grams.
b. Between 318.25 grams and 331.75 grams.
c. Above 316.59 grams.
d. Below 312.2 grams
Step-by-step explanation:
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the z-score of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Mean of 325 grams and a standard deviation of 10 grams.
This means that [tex]\mu = 325, \sigma = 10[/tex]
a. Highest 10 percent
This is X when Z has a pvalue of 1 - 0.1 = 0.9, so X when Z = 1.28.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]1.28 = \frac{X - 325}{10}[/tex]
[tex]X - 325 = 10*1.28[/tex]
[tex]X = 337.8[/tex]
So 337.8 grams.
b. Middle 50 percent
Between the 50 - (50/2) = 25th percentile and the 50 + (50/2) = 75th percentile.
25th percentile:
X when Z has a pvalue of 0.25, so X when Z = -0.675.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]-0.675 = \frac{X - 325}{10}[/tex]
[tex]X - 325 = -0.675*10[/tex]
[tex]X = 318.25[/tex]
75th percentile:
X when Z has a pvalue of 0.75, so X when Z = 0.675.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]0.675 = \frac{X - 325}{10}[/tex]
[tex]X - 325 = 0.675*10[/tex]
[tex]X = 331.75[/tex]
Between 318.25 grams and 331.75 grams.
c. Highest 80 percent
Above the 100 - 80 = 20th percentile, which is X when Z has a pvalue of 0.2. So X when Z = -0.841.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]-0.841 = \frac{X - 325}{10}[/tex]
[tex]X - 325 = -0.841*10[/tex]
[tex]X = 316.59[/tex]
Above 316.59 grams.
d. Lowest 10 percent
Below the 10th percentile, which is X when Z has a pvalue of 0.1, so X when Z = -1.28.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]-1.28 = \frac{X - 325}{10}[/tex]
[tex]X - 325 = -1.28*10[/tex]
[tex]X = 312.2[/tex]
Below 312.2 grams
