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# s2 queries watch

1. 5. As part of a business studies project, 8 groups of students are each randomly allocated
10 different shares from a listing of over 300 share prices in a newspaper. Each group has to
follow the changes in the price of their shares over a 3-month period.
At the end of the 3 months, 35% of all the shares in the listing have increased in price and the rest have decreased.
Find the probability that, for the 10 shares of one group:
more than 5 have gone down in price.
For this one i assumed that if more than 5 have gone down in price then less than or equal to 5 have gone up so i found the prob of less than or equal to 5 going down in price and then took it away from 1....but my answer is wrong. Would i have to use (10,0.65)binomial and work it out separately, or is their another way?

Also
A teacher wants to investigate the sports played by students at her school in their free time.
She decides to ask a random sample of 120 pupils to complete a short questionnaire.
The teacher believes that 1 in 20 of the students play tennis in their free time. She uses the
data collected from her sample to test if the proportion is different from this.
(c) Using a suitable approximation and stating the hypotheses that she should use, find the
critical region for this test. The probability for each tail of the region should be as close
as possible to 5%.

I found that po(6). Then i worked out that p(x<=c1)<=0.05....so c1 is 1 when i looked at the poisson cumulative distribution function. 1 is 0.0174 this is the highest value which is less than or equal to 0.05 but the answer says it should be 2 which is 0.0620( this is above 0.05) even though closer. My teacher told me it always has to be less than or equal to....is this the case or is it just the value that is closest to the tail?
2. (Original post by MIKE ESSIEN IS QUITE SICK)
My teacher told me it always has to be less than or equal to
this is usually the case, but sometimes the question states "The probability for each tail of the region should be as close
as possible to 5%", in which case you find the closest value
3. can anyone help?
4. more than five have have gone down. that means either 6 or 7, 8 .....have gone down.

therefore 4, or 3 or 2.... have gone up

X¬B(10, 0.35)

P(x<=4)=?
5. for part c).

in this critical region thing, you get the 2 values of x which is 1. just less than 0.05 and 2. just greater than 0.05. then check the one closer to 0.05

in this case, 2 is closer and therefore the correct answer for the lower CR
6. (Original post by kosy91)
more than five have have gone down. that means either 6 or 7, 8 .....have gone down.

therefore 4, or 3 or 2.... have gone up

X¬B(10, 0.35)

P(x<=4)=?
ye is it less than or equal to 4 and not 5?
7. (Original post by MIKE ESSIEN IS QUITE SICK)
ye is it less than or equal to 4 and not 5?
less than or equal to 4
8. (Original post by kosy91)
less than or equal to 4
i meant why is it less than or equal to 4 and not less than or equal to 5
9. i have explained earlier also. greater then give means a probability of greater than or equal to 6. that means a probability of less than equal 4 of going up

or

more than five going up is the same as less than 5 going down. less than five going down is the same as less than equal to 4 going down

so it comes down to the same thing

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