If you roll two fair six-sided dice, what is the probability that the sum is 5 or lower?
2 answers:
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In order to solve this problem easily you coin this method: Find the squares of 0.13 and 0.14. They are respectively 0.0169 and 0.0196. Irrational numbers are going to located between this interval, considering that we are not counting perfect squares. 
are the three possible answers.
Answer:
There is an 38.21% probability that we find this lifespan for our sample average, or something even shorter.
Step-by-step explanation:
Problems of normally distributed samples can be 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.
In this problem, we have that:
A manufacturing firm claims that the batteries used in laptop computers will last an average of 50 months. This means that .
We found that the sample had a average lifespan of 47.3 months, and a standard deviation of s = 9 months. What is the probability that we find this lifespan for our sample average, or something even shorter?
We have to find the pvalue of Z when .
We are working with a sample mean, so we use the standard deviation of the sample in the place of . That is
So
has a pvalue of 0.3821.
There is an 38.21% probability that we find this lifespan for our sample average, or something even shorter.