Statistics question on simple random sampling?

Statistics question on simple random sampling?

Postby caries16 » March 19th, 2014, 4:05 am

i just cant find a formula to do this

The weight of medium-size tomatoes selected at random from a bin at the local supermarket is a
random variable with mean ? = 10 oz. and standard deviation ? = 1 oz.

Suppose we pick four tomatoes from the bin at random and put them in a bag. Define
the random variable Y = the weight of the bag containing the four tomatoes. What is the
standard deviation of the random variable Y?
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caries16
 
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Statistics question on simple random sampling?

Postby truesdale29 » March 19th, 2014, 4:05 am

i just cant find a formula to do this

The weight of medium-size tomatoes selected at random from a bin at the local supermarket is a
random variable with mean ? = 10 oz. and standard deviation ? = 1 oz.

Suppose we pick four tomatoes from the bin at random and put them in a bag. Define
the random variable Y = the weight of the bag containing the four tomatoes. What is the
standard deviation of the random variable Y?
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truesdale29
 
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Joined: March 21st, 2012, 6:03 am

Statistics question on simple random sampling?

Postby dong » March 19th, 2014, 4:15 am

(assuming the bag itself weighs nothing)

Variance of the weight of the bag of tomatoes = 4 x variance of weight of 1 tomatoes = 4 ?^2 = 4 oz^2

Hence s.d. of weight of bag of tomatoes = 2 oz.
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