test #4- Normal Distribution

Question 1

what are the percentages on a normally distributed graph

Answer 1

2.5%
13.5%
34%
34%
13.5%
2.5%

Question 2

what are critical values

Answer 2

mean +/- SD

Question 3

what is skewness

Answer 3

when the bell curve is not perfect

Question 4

characteristics of left/negatively skewed:

Answer 4

-Left tailed
- Mean < median
-more variety in values that are less than the median

Question 5

characteristics of right/positively skewed:

Answer 5

-right tailed
-Mean > median
- More variety in values that are greater than the median

Question 6

Pearson’s index;
and what results mean

Answer 6

[3(mean-med) ] / s.d
Positive= right-tailed/ positive skew
negative= left-tailed/ negative skew

Question 7

how significant can a skew be

Answer 7

[-1,1] is not a significant skew

Question 8

graph for z scores

Answer 8

• bell shaped
• mean=0
• s.d = 1

Question 9

what do we use z scores for

Answer 9

to compare data sets

Question 10

z scores to identify unusual values

Answer 10

]-2 and less): unusual
(-2 to 2): usual
]2 to more): unusual

Question 11

how to find a percent given a value

Answer 11

normal cdf(lower, upper, mean, s.d.)

Question 12

how to identify a value given a percent

Answer 12

inv norm (area, mean, sd)

the area is % as decimal

Question 13

box plot to prove normalcy

Answer 13

left skew at the right
normal in the middle
right skew at the left

Question 14

proving normalcy with mean vs median

Answer 14

mean< median= left skewed
mean= median= normal
mean> median = right skewed

Question 15

proving normalcy with Pearson’s index

Answer 15

sk< 0= left skewed
sk= 0= normal
sk> 0= right skewed