Question

A study of persons (N=1170) indicted for murder in Kentucky revealed that each individual had an average number of 1.69 prior felony arrests. The standard deviation was 2.6 (20 points).

a. calculate the 95 percent confidence interval for this distribution and write a statement about what it represents.

b. determine the z score for a murder defendant who had two prior felony arrests. Under the normal curve, what statement could you make about this z score?

An expert already answered but it is difficult for me to see his or her writing and he or her did not write the two statements required. Please can you help me?

I need a better writing and the two statements

Answer 1

Answer :

Given data is :

Sample size N = 1170

Mean = = 1.69

Standard deviation = = 2.6

a)Given confidence interval = 95%

Z value at 95% = 1.96

therefore,

CI =

=

=

=

=

=

=

CI = (1.541 , 1.839)

Key points :

1)A confidnece interval computes the probability that a population parameter will fall between two set of values.

2)CI measure the level of uncertainity and certainty in a sampling method.

3)Frequently, CI reflect certainty levels of 95% or 99%.

Conclusion :

From the above answer,at 95% confidence interval the study of persons indicted for murder in Kentucky revealed that each individual had prior felony arrests values lies between 1.541 to 1.839.

b)From the given data,the  two prior felony arrests.

i.e x = 2

Z =

Now substitute all values in above formula,we get

Z = (2 - 1.69) / 2.6

= 0.31 / 2..6

= 0.1192

Z = 0.1192

Key points :

1)A z-score portrays the situation of a raw score as far as its good ways from the mean, when estimated in standard deviation units. The z-score is +ve if value lies over the mean, and negative in the event that it lies below the mean.

2)The estimation of the z-score tells you what number of standard deviations you are away from the mean. On the off chance that a z-score is equivalent to 0, it is on the mean.

3)A positive z-score shows the raw score is higher than the mean avg. For instance, if a z-score is equivalent to +1, it is 1 standard deviation over the mean.

4)A negative z-score uncovers the raw score is below the mean normal. For instance, if a z-score is equivalent to - 2, it is 2 standard deviations below the mean.

Conclusion :-

z-score for a murder respondent who had prior felony arrests is determined as 0.1192. which is sure so we conclude that under the normal curve,z-score is 0.1192 standard deviation over the mean (right to the mean).