the table shows the number of minutes Tim has for lunch and study hall. he calculates that these two periods account for 18% of
the minutes he spends at school .how many minutes does he spend at school?
1 answer:
Tim spends 500 minutes at the school.
Step-by-step explanation:
Given,
Time for lunch = 45 minutes
Time for study hall = 45 minutes
Total = 45+45 = 90 minutes
This represents 18% of the total minutes Tim spend at school.
Let,
x be the total minutes Tim spend at school.
18% of x = 90 minutes
Dividing both sides by 0.18
Tim spends 500 minutes at the school.
Keywords: percentage, division
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Answer:
a) The sample is larger than 30, so, by the Central Limit Theorem, the distribution of the sample means will be normally distributed with mean 38.4 and standard deviation 0.8538.
b) 0.25% probability that his average kicks is less than 36 yards
c) 0.11% probability that his average kicks is more than 41 yards
d-a) The sample is larger than 30, so, by the Central Limit Theorem, the distribution of the sample means will be normally distributed with mean 38.4 and standard deviation 1.08
d-b) 1.32% probability that his average kicks is less than 36 yards
d-c) 0.80% probability that his average kicks is more than 41 yards
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 normally distributed samples are solved using 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.
In this problem, we have that:
a. What is the distribution of the sample mean? Why?
The sample is larger than 30, so, by the Central Limit Theorem, the distribution of the sample means will be normally distributed with mean 38.4 and standard deviation 0.8538.
b. What is the probability that his average kicks is less than 36 yards?
This is the pvalue of Z when X = 36. So
By the Central Limit Theorem
has a pvalue of 0.0025
0.25% probability that his average kicks is less than 36 yards
c. What is the probability that his average kicks is more than 41 yards?
This is 1 subtracted by the pvalue of Z when X = 41. So
has a pvalue of 0.9989
1 - 0.9989 = 0.0011
0.11% probability that his average kicks is more than 41 yards
d. If the sample size is 25 in the above problem, what will be your answer to part (a) , (b)and (c)?
Now
So
a)
The sample is larger than 30, so, by the Central Limit Theorem, the distribution of the sample means will be normally distributed with mean 38.4 and standard deviation 1.08
b)
has a pvalue of 0.0132
1.32% probability that his average kicks is less than 36 yards
c)
has a pvalue of 0.9920
1 - 0.9920 = 0.0080
0.80% probability that his average kicks is more than 41 yards