Answer: 260 gallons
Step-by-step explanation:
We can use a proportion to solve this problem. We know that a family used 15 gallons of milk every 3 weeks. Since the problem asks for how much they will need for a year, we can gather that a year is 52 weeks. We can come up with the following proportion.
[cross multiply]
[divide both sides by 3]
Therefore, they will need to purchare 260 gallons.
Answer:
0.7780
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal probability distribution
When the distribution is normal, we use the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
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 pvalue, 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 and standard deviation
, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean
and standard deviation
.
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
Population:
We have that
Sample of 12:
What is the probability that the mean cost will be more than $7.00?
This is 1 subtracted by the pvalue of Z when X = 7. So
By the Central Limit Theorem
has a pvalue of 0.222
1 - 0.222 = 0.778
So the answer is 0.7780