Question

1.

How do you know when to use the binomial distribution to model a situation? [4 bullets]

2.

How do you know when to use =NORMDIST versus when to use =NORMINV? [2 sentences]

3.

What are the two ways that the distribution of sample means can be approximately normal? [2 bullets]

Answer 1

(1)

The Binomial Distribution can be used to model a situation under the following conditions:

(i) The number of Trials = n is fixed

(ii) Each Trial is independent

(iii) Each Trial has one of 2 mutually exclusive outcomes, called success and failure

(iv) The probability of success = p is same for all trials

(2)

(i) The function NORMDIST is used to obtain the normal cumulative distribution for the specified mean and standard deviation. The Syntax of the function NORMDIST is:
NORMINV (x, mean, standard-deviation, cumulative-flag)

(ii) The function NORMINV is used to obtain the inverse of the normal cumulative distribution for the specified mean and standard deviation. The Syntax of the function NORMINV is:
NORMINV (probability, mean, standard-deviation)

(3)

The distribution of sample means can be approximately normal under the following two ways:
(i) When the population Standard Deviation () is known, The distribution of sample means is normal irrespective of sample size.

(ii) When the Sample Size = n > 30, for large sample, the distribution of sample means can be approximately normal irrespective of the shape of the population.