Stats 1201 Early

Question 1

Can there be partial association?

Answer 1

Yes

Question 2

Does this produce N?

Answer 2

Yes

Question 3

Is this the equation for the mean?

Answer 3

No, that is the standard deviation.

Question 4

Does this equal 0?

Answer 4

No, because this is squared. The squaring removes minuses, so they don’t cancel out positive numbers.

Question 5

What is the expected value of y in this situation?

Answer 5

No correlation, therefore the best we can do is the mean of y as a prediction.

Question 6

Positive or negative association?

Answer 6

Negative association (and it isn’t a perfect association)

Question 7

Is this a negative association?

Answer 7

No it is a positive association

Question 8

What type of skew is represented here?

Answer 8

No skew

Question 9

What type of skew is represented here?

Answer 9

Right skew

Question 10

What type of skew is represented?

Answer 10

Right skew

Question 11

Is this an instance of right skew?

Answer 11

Left skew

Question 12

What is the interpretation of s?

Answer 12

This is the sample standard deviation of y. It is the typical distance scores have from the mean.

Question 13

Is this a measure of central tendency or of dispersion?

Answer 13

Spread, dispersion. It is standard deviation (and the word “deviation” says it all).

Question 14

With a right skewed distribution would you expect anomalously high or low scores?

Answer 14

High scores

Question 15

With a left skewed distribution would you expect anomalously high or low scores?

Answer 15

Low scores

Question 16

Which is most stringent, a significance criterion of .05 or .01?

Answer 16

.01 means you have to have, say, a bigger difference between means of distributions or a higher correlation to achieve significance.

Question 17

This shows the number of croissants eaten per month. What is the IQR?

Answer 17

The IQR is Q3-Q1, which is about 12.0 - 2.6, or 9.4 croissants. The units are croissants here . . .

Question 18

Given the following sample observations of minutes taken for a subway to get to a particular station, provide an estimate of the actual standard deviation:

Answer 18

So 2.1 minutes is our standard deviation estimate

Question 19

Everyone at your company is given a year-end bonus of $1,500! WOW!! How will this affect the mean? How will this change the standard deviation of salaries?

Answer 19

Since the salaries all increased, the mean will increase by $1,500. However, since all the salaries increase by exactly the same amount, the difference between each salary and the mean will be exactly as before (the mean increases but so do the salaries so the differences between the mean and the salaries don’t change).

Question 20

What 2 numbers form the second quartile for the following?
1, 3, 2, 4, 5, 6, 7, 8

Answer 20

3,4 form the second quartile (order the numbers first)

Question 21

For the following what is the median?
4, 5, 11, 9, 12, 20

Answer 21

First order the distribution:
4 7 9 11 12 20

SO the median is (9+11)/2 = 10

Question 22

Can IQR be negative?

Answer 22

No, it is telling you the distance numerically between two numerical reference points. It is a distance measure - so even if it is the distance between two negative numbers it is a positive distance.

Question 23

Can we use the IQR to check for indications of normality?

Answer 23

Yes!

Question 24

Calculate the Q1 using the TI-method and also using the Text-method:

Answer 24

Question 25

25% of the delay times for the Nanaimo run are less than how many minutes?

Answer 25

2.5 minutes

Question 26

mean=20 median=34 Is this a normal distribution?

Answer 26

No, in a normal distribution we'd expect the median and mean to be about the same.

Question 27

mean=20 median=34 Is there skew and if so, what kind of skew?

Answer 27

There appears to be skew. The mean is lower, which means (because it is sensitive to size of the scores and not to the position) that low scores are dragging it down from the typical value. So it is left skewed.