To the nearest percent what is the probability that a student who failed the exam got less than 6 hours of sleep

Mathematics

1 answer:

Anarel [89]3 years ago

8 0

In order to study the relationship between the amount of sleep a student gets and his or her school performance, a researcher collected data from 120 students. The two-way frequency table shows the number of students who passed and failed an exam and the number of students who got more or less than 6 hours of sleep the night before.
<span>The probability that a student who failed the exam got less than 6 hours of sleep can be calculated as:
</span>
Let,
L be the event of getting less than 6 hours of sleep
F be the event of failing the exam.
Then,
P(L and F) = n(L∩F) ÷ n(F)
= (10 ÷ 18) × 100%
= 5 ÷ 9 × 100%
= 55.55%

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???? I’m very confused

Liono4ka [1.6K]

C; 120 because 24x=360 so x=15. Then ABC is 8x, so 8*15=120.

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4 years ago

A large manufacturing plant uses lightbulbs with lifetimes that are normally distributed with a mean of 1200 hours and a standar

a_sh-v [17]

Answer:

The bulbs should be replaced each 1060.5 days.

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

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:

$\mu = 1200, \sigma = 60$