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3 years ago

A set of history exam scores are normally distributed with a mean of 83.2 points and a standard deviation

Mathematics

1 answer:

jek_recluse [69]3 years ago

3 0

Answer: .3330

Step-by-step explanation:

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When a certain type of thumbtack is flipped, the probability of its landing tip up (U) is 0.66 and the probability of its land

valina [46]

Answer: There are 4 possibilities. They are all listed below with their percents.

You can create a tree diagram to shows all of the possibilities. It will start with 2 branches and then each of those branches will have 2 branches.

The possibilities are: UU, UD, DU, DD

To find the probabilities of each, you have to multiply the percent for each together.

UU = 0.66 x 0.66 = 0.4356
UD = 0.66 x 0.34 = 0.2244
DU = 0.34 x 0.66 = 0.2244
DD = 0.34 x 0.34 = 0.1156

6 0

3 years ago

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The manager of a fleet of automobiles is testing two brands of radial tires and assigns one tire of each brand at random to the

Darya [45]

Answer:

Brand 1 Brand 2 Difference

37734 35202 2532

45299 41635 3664

36240 35500 740

32100 31950 150

37210 38015 −805

48360 47800 560

38200 37810 390

33500 33215 285

Sum of difference = 2532+ 3664+740+150 −805+ 560 +390 +285 = 7516

Mean = $d=\frac{7516}{8}$

Mean = $d=939.5$

a) d= 939.5

$\text{Sample Standard deviation, s} = \sqrt{\dfrac{(x-\bar{x})^2}{n-1}}$

$=\sqrt{\dfrac{(2532-939.5)^2+(3664-939.5)^2+(740-939.5)^2 ...+(285-939.5)^2}{8-1}}$

=1441.21

b)SD= 1441.21

c)Calculate a 99% two-sided confidence interval on the difference in mean life.

confidence level =99%

significance level =α= 0.01

Degree of freedom = n-1 = 8-1 =7

So, $t_{\frac{\alpha}{2}}=3.499$

Formula for confidence interval $= \left( \bar{X} \pm t_{\frac{\alpha}{2}} \times \frac{s}{\sqrt{n}} \right)$

Substitute the values

confidence interval $= 939.5 \pm 3.499 \times \frac{1441.21}{\sqrt{8}} \right)$

confidence interval $= 939.5 - 3.499 \times \frac{1441.21}{\sqrt{8}} \right)$ to $= 939.5 + 3.499 \times \frac{1441.21}{\sqrt{8}} \right)$

Confidence interval $−843.396\$ to $2722.396$

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