Module 15: Inferential statistics

Question 1

What is the difference between descriptive statistics and inferential statistics?

Answer 1

Descriptive statistics is summarizing or describing data from popylations and inferential stats is maing inferences from distributions (analyze samplings to make predictions about larger populations)

Question 2

The normal distribution

Answer 2

Desccribes a very common probability distribution of values of a continous variable around the mean, no skew

Question 3

Graph of a normal distribution is called

Answer 3

The normal curve

Question 4

Vertical axis of the normal curve

Answer 4

Frequency of values

Question 5

Horizontal axis of the normal curve

Answer 5

Scale of continous values, what we are measuring

Question 6

Properties of a normal distribution (4)

Answer 6

• symmetrical
• unimodal
• bell shaped curve
• mean mode and median are equal

Question 7

Spread of normal distribution is determined by—– larger spread means —–

Answer 7

standard deviation
larger SD

Question 8

About —% of the data lie within 1 SD of the mean

Answer 8

68%

Question 9

About —% of the data lie within 2 SD of the mean

Answer 9

95%

Question 10

About —% of the data lie within 3 SD of the mean

Answer 10

99.7%

Question 11

The standard normal distribution

Answer 11

A normal distribution with a mean of 0 and a standard deviation of 1

Question 12

Properties of the standard normal deviation (2)

Answer 12

• The cumulative area is close to 0 for Z scores close to z=+/- 3.49
• The cumulaytive area increases as the Z score increases

Question 13

Z-table

Answer 13

Table with pre-calculated areas under the curve up to each value for Z for a standard normal distribution

Question 14

Standardization+formula (2)

Answer 14

Turning data into a standard normal distribution
- use the formula z=(x-mean)/SD

Question 15

If you are trying to find the Z score for anything below the mean, your 2 scores should be

Answer 15

negative

Question 16

a Z score of -3.45 means

Answer 16

more than 3 SD below the mean

Question 17

Z score tells us

Answer 17

how many units you go above and below the SD

Question 18

Larger proportion is —- side for + Z score and —- for - Z score

Answer 18

• left
• right

Question 19

Percentile always mean

Answer 19

everything from the far most left side until that said percetile.

Question 20

Areas are never

Answer 20

> 1

Question 21

sampling error

Answer 21

Random variability between observations or statistics that is simply due to chance

Question 22

Sampling Distribution + formed when (2)

Answer 22

• The distribution of a statistic over repeated sampling from a specified population
• Formed when samples of sample size n are repeatedly taken from a population

Question 23

The central limit theorem

Answer 23

The larger the sample size that we draw from a population the more normal the sampling distribution of the sample mean becomes, regardless of the shape of population

Question 24

If we take samples of this distribution, cailate their means and then graph them as long as those sampels are big enough >=30, then when we graph that sample distribution it would be —- and centered around —-

Answer 24

• normally distributed
• population mean

Question 25

Greater the sample size, the more precise/less variability in the

Answer 25

sample means

Question 26

You can only use Zed tables when

Answer 26

it is normally distributed

Question 27

If the population itself is normally distributed, the sampling distribution of the sample means is —– for any —-

Answer 27

• normally distributed
• sample size n

Question 28

In both case where you have sample >=30 or a normal distribution, according to the CLT, the sampling distribution of sample means has (3):

Answer 28

1. A mean equal to the population mean
2. A variance equal to 1/n times the variance of the population
3. A standard deviation equal to the population SD divided by the square root of n

Question 29

SD and variane of pop and sample formulas:

Answer 29

Question 30

Zed score formula for transforming single scores and sample mean into a zed score:

Answer 30