![jaxheisjax532](/avatars/43643.jpg)
jaxheisjax532
19.10.2019 •
Mathematics
Heppp hep
ying made a scale drawing of a house and its lot.the lawn in the backyard is 90 centimeters long in the drawing.the actual lawn is 60 meters long.what scale did ying use?
3 centimeters = blank metes
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Ответ:
Ответ:
0.4332 = 43.32% probability that the sample mean is between 21 and 22.
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
and standard deviation
, the z-score 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 p-value, we get the probability that the value of the measure is greater than X.
Central Limit Theorem
The Central Limit Theorem establishes 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.
According to a report from a business intelligence company, smartphone owners are using an average of 22 apps per month.
This means that![\mu = 22](/tpl/images/1349/9645/7706b.png)
Standard deviation is 4:
This means that![\sigma = 4](/tpl/images/1349/9645/1e788.png)
Sample of 36:
This means that![n = 36, s = \frac{4}{sqrt{36}}](/tpl/images/1349/9645/52c47.png)
What is the probability that the sample mean is between 21 and 22?
This is the p-value of Z when X = 22 subtracted by the p-value of Z when X = 21.
X = 22
By the Central Limit Theorem
X = 21
0.5 - 0.0668 = 0.4332
0.4332 = 43.32% probability that the sample mean is between 21 and 22.