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Sagot :
Answer:
0.0571 = 5.71% probability that this fund-raising event is a success
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
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.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
The organizers would call this event a success if the total contributions exceed $4,600
Forty families, so sample mean above 4600/40 = 115.
Mean and a standard deviation of $105 and $40
This means that [tex]\mu = 105, \sigma = 40[/tex]
Sample of 40
This means that [tex]n = 40, s = \frac{40}{\sqrt{40}} = 6.3246[/tex]
What is the probability that this fund-raising event is a success?
Sample mean above 115, which is 1 subtracted by the pvalue of Z when X = 115. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
By the Central Limit Theorem
[tex]Z = \frac{X - \mu}{s}[/tex]
[tex]Z = \frac{115 - 105}{6.3246}[/tex]
[tex]Z = 1.58[/tex]
[tex]Z = 1.58[/tex] has a pvalue of 0.9429
1 - 0.9429 = 0.0571
0.0571 = 5.71% probability that this fund-raising event is a success
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