PLEASE HELP IM BEGGING YOU ITS DUE IN 15 MIN ILL GIVE BRAINEST AND PTS
1 answer:
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Answer:
Step-by-step explanation:
Given that a fair coin is flipped twelve times.
It means the number of possible sequences of heads and tails would be:
2¹² = 4096
We can determine the number of ways that such a sequence could contain exactly 9 tails is the number of ways of choosing 9 out of 12, using the formula
Plug in n = 12 and r = 9
∵
∵
Thus, the probability will be:
Thus, the probability of the coin landing tails up exactly nine times will be:
Answer:
The bulbs should be replaced each 1436.9 hours.
Step-by-step explanation:
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.
In this problem, we have that:
How often should the bulbs be replaced so that no more than 1% burn out between replacement periods?
This is the first percentile of hours. So it is X when Z has a pvalue of 0.01.
So it is X when Z = -2.33.
The bulbs should be replaced each 1436.9 hours.