Statistics & Probability
posted by Alia .
If X is a normal random variable with mean 11, and if the probability that X is less than 12.10 is .72 , then what is the standard deviation of X?
Select one:
a. 3.00
b. 6.25
c. 2.50
d. 1.25
Please note that the answer for the above is stated as c.2.50. However, my answer comes to 1.89 which is not given as an option and I can't figure out where I'm going wrong so please can anyone help me with this problem.
Thanks.
Respond to this Question
Similar Questions

Statistics
1) A Motor Company has purchased steel parts from a supplier for several years and has found that 10% of the parts must be returned because they are defective. An order of 25 parts is received. What are the mean and standard deviation … 
Statistics
Suppose that the probability distribution of a random variable x can be described by the formula P(x) = x/15 For each of the values x = 1, 2, 3, 4, and 5. For examples, then, p(x=2) = p(2) = 2/15 a Write out the probability distribution … 
Statistics
Suppose that the probability distribution of a random variable x can be described by the formula P(x) = x/15 For each of the values x = 1, 2, 3, 4, and 5. For examples, then, p(x=2) = p(2) = 2/15 a Write out the probability distribution … 
STATISTICS
Consider a binomial random variable where the number of trials is 12 and the probability of success on each trial is 0.25. Find the mean and standard deviation of this random variable. I have a mean of 4 and a standard deviation of … 
Statistics and Probability
A computer supply house receives a large shipment of blank CDs each week. Past experience has shown that the number of flaws per CD can be described by the following probability distribution, where the random variable X represents … 
statistics
Let x be a continuous random variable that is normally distributed with a mean of 65 and a standard deviation of 15. Find the probability that x assumes a value less than 44. 
statistics
Let x be a continuous random variable that is normally distributed with a mean of 65 and a standard deviation of 15. Find the probability that x assumes a value less than 45. 
probability
A random experiment of tossing a die twice is performed. Random variable X on this sample space is defined to be the sum of two numbers turning up on the toss. Find the discrete probability distribution for the random variable X and … 
statistics
Let x be a continuous random variable that is normally distributed with a mean of 65 and a standard deviation of 15. Find the probability that x assumes a value less than 44. 
Probability
If X is a normal random variable with mean 11, and if the probability that X is less than 12.10 is .72 , then what is the standard deviation of X?