Author Topic: S1 and S2 DOUBTS HERE!!!!  (Read 62852 times)

Offline narnia

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Re: S1 DOUBTS HERE!!!!
« Reply #165 on: April 21, 2011, 09:00:28 pm »
a fair dice is thrown once. what is the probability that the score is greatr than 3 or a prime number or both?
i added 3/6 + 3/6 + ( 3/6*3/6) , my ans being 5/4 wherews ans given is 5/6 =s

Offline EMO123

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Re: S1 DOUBTS HERE!!!!
« Reply #166 on: April 22, 2011, 12:19:51 pm »
a fair dice is thrown once. what is the probability that the score is greatr than 3 or a prime number or both?
i added 3/6 + 3/6 + ( 3/6*3/6) , my ans being 5/4 wherews ans given is 5/6 =s

(x>3)=4,5,6
p of (x>3)=3/6
(x a prime number)= 2,3,5,   
p of (x a prime number)
So both =2,3,5 and 4,5,6

5 is repeated so (2,3,4,5,6)=p of both 5/6
the Question was to confuse you .

Offline ashish

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Re: S1 DOUBTS HERE!!!!
« Reply #167 on: April 24, 2011, 07:29:03 am »
rex has an old car. the probability that he is able to start the car on a rainy day is 0.2 and the probability that he is able to start it on a fine day is 0.6 . if the weather is either fine or rainy, and probability the weather is fine is p, the find in terms of p
1) the probability that he is unable to start the car on a day
2) the conditional probability that a day is fine and he is unable to start the car?

can someone solve this question please ???

Offline astarmathsandphysics

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Re: S1 DOUBTS HERE!!!!
« Reply #168 on: April 24, 2011, 08:57:01 am »
One mo

Offline astarmathsandphysics

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Re: S1 DOUBTS HERE!!!!
« Reply #169 on: April 24, 2011, 09:09:59 am »
prob solved in attachment

Offline EMO123

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Re: S1 DOUBTS HERE!!!!
« Reply #170 on: April 24, 2011, 09:38:11 am »

Offline astarmathsandphysics

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Re: S1 DOUBTS HERE!!!!
« Reply #171 on: April 24, 2011, 10:31:46 pm »
No probs

Offline Malak

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Re: S1 DOUBTS HERE!!!!
« Reply #172 on: April 30, 2011, 04:02:50 pm »
Need help with this question

Part (e) to find median
I know we use interpolation but i am confused with the values to use for the upper/lower cumulative frequency..
thx

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Offline mdwael

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Re: S1 DOUBTS HERE!!!!
« Reply #173 on: May 01, 2011, 11:12:58 am »
Need help with this question

Part (e) to find median
I know we use interpolation but i am confused with the values to use for the upper/lower cumulative frequency..
thx

This is S1 Q5 from 2007 Jun


First of all make a cumulative frequency table.

you have a total of 100. Thus median should be the 50th entry.. so when you make the cf you will find the the 50th tab lies in 14-18 class and Cf is 26-50.. here it is not neccessary to do interpolation because 50 is the last one in the class so you can directly pick median of t is 18 seconds. but you can still do interpolation to check your answer.


    (X - 14) / 18-14 = 50-26 / 50 -26

X-14 / 4 = 1

X-14 = 4

X = 14 + 4 = 18


In the same manner u find the quartiles... since the  total frequency is 100 so lower quartile is 100/4 = 25 and upper is 100*3/4 = 75th entry
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Offline mdwael

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Re: S1 DOUBTS HERE!!!!
« Reply #174 on: May 01, 2011, 11:22:29 am »
I have a question regarding Normal Distribution..

I understand how to get and find probabilities but how do you find the mean and standard deviation when the lower quartile and upper quaritle are given? like in this question..

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Offline Aadeez || Zafar

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Re: S1 DOUBTS HERE!!!!
« Reply #175 on: May 01, 2011, 02:18:28 pm »
in normal distribution,
median =means

and so median= (LQ+UQ)/2

using mean value find s.d



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Offline Arthur Bon Zavi

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Re: S1 DOUBTS HERE!!!!
« Reply #176 on: May 03, 2011, 10:31:04 am »
in normal distribution,
median =means

and so median= (LQ+UQ)/2

using mean value find s.d

BOLD - How can this be possible ?

Take upper quartile as 75 % (probability of 0.75) OR lower quartile as 25 % (probability of 0.25). Though I recommend you to take 0.75 because for LOWER QUARTILE (0.25) you have to do a bit of more subtraction which will be confusing.

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Offline xMilishax

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Re: S1 DOUBTS HERE!!!!
« Reply #177 on: May 17, 2011, 02:05:59 pm »
Can someone help me solve:
May 2010 Q7 Part (b)?

I'm kinda confused with Normal distribution.

Thanks.  :)

Offline Arthur Bon Zavi

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Re: S1 DOUBTS HERE!!!!
« Reply #178 on: May 17, 2011, 02:12:07 pm »
Quote
Can someone help me solve:
May 2010 Q7 Part (b)?

I'm kinda confused with Normal distribution.

Thanks.  :)

Variant ?

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Offline xMilishax

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Re: S1 DOUBTS HERE!!!!
« Reply #179 on: May 17, 2011, 02:25:24 pm »