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Answer:
0.3874 = 38.74% probability that exactly 9 of the 10 consumers recognize her brand name.
0.6126 = 61.26% probability that the number who recognize her brand name is not nine.
Step-by-step explanation:
For each consumer, there are only two possible outcomes. Either they recognize the name, or they do not. The probability of a customer recognizing the name is independent of anu other customer. This means that the binomial probability distribution is used to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
The brand name of Mrs. Fields (cookies) has a 90% recognition rate.
This means that .
Sample of 10
This means that
Find the probability that exactly 9 of the 10 consumers recognize her brand name.
This is P(X = 9). So
0.3874 = 38.74% probability that exactly 9 of the 10 consumers recognize her brand name.
Also, find the probability that the number who recognize her brand name is not nine.
1(100%) subtracted by those who recognize. So
1 - 0.3874 = 0.6126
0.6126 = 61.26% probability that the number who recognize her brand name is not nine.
Answer:
And if we solve for a we got
So the value of height that separates the bottom 10% (Fastest 10%) of data from the top 90% is 393.2.
so if the time is 393.2 or lower a boy would earn a certificate of recognition from the fitness association
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the time for this event of a population, and for this case we know the distribution for X is given by:
Where and
NOTE: For this case the fastest 10% is on the lower tail of the distribution
For this part we want to find a value a, such that we satisfy this condition:
(a)
(b)
Both conditions are equivalent on this case. We can use the z score again in order to find the value a.
As we can see on the figure attached the z value that satisfy the condition with 0.1 of the area on the left and 0.9 of the area on the right it's z=-1.28. On this case P(Z<-1.28)=0.1 and P(z>-1.28)=0.9
If we use condition (b) from previous we have this:
But we know which value of z satisfy the previous equation so then we can do this:
And if we solve for a we got
So the value of height that separates the bottom 10% (Fastest 10%) of data from the top 90% is 393.2.
so if the time is 393.2 or lower a boy would earn a certificate of recognition from the fitness association