Statistics

Question 1

Why should you study Statistics?

Answer 1

• objective evaluation of numbers
• population description
• estimate unknown values

Question 2

What is population description?

Answer 2

a sample statistic to make inferences for a population because it is hard to count/analyze entire population

Question 3

What is estimate unknown value?

Answer 3

breeding value

Question 4

What is the most important value? Why?

Answer 4

breeding value; part of genetic variance that is passed from parent to offspring

Question 5

What is an example of population desciption?

Answer 5

backfat thickness in Hampshire hogs

Question 6

What is the formula for genetic variance?

Answer 6

Vg=Bv + GCV

Question 7

Why do we need to measure traits?

Answer 7

• variation

- “raw material” breeder has available for herd improvement

Question 8

What traits are the easiest to improve?

Answer 8

traits with highest variability

Question 9

What type of traits are discontinuous variation?

Answer 9

qualitative traits

Question 10

Are qualitative traits affected by the environment?

Answer 10

no

Question 11

How many genes control qualitative traits?

Answer 11

one or few

Question 12

What type of traits are continuous variation?

Answer 12

quantitative traits

Question 13

How many genes control quantitative traits?

Answer 13

many genes

Question 14

Is continuous variation simple or complex?

Answer 14

highly complex

Question 15

Are discontinuous variation traits or continuous variation traits economically important?

Answer 15

continuous variation

Question 16

What is a quality of continuous variation?

Answer 16

many small gradations almost imperceptible to one another

Question 17

Are samples taken from a population random or specific?

Answer 17

random

Question 18

How are continuous variation traits highly complex?

Answer 18

a matter of genotype and environment interaction

Question 19

What is the point of taking a sample?

Answer 19

to make inferences about a population

Question 20

How would weaning weight in cattle be inferred?

Answer 20

take a random sample, analyze data, and then infer weaning weight of the population

Question 21

What is population parameter?

Answer 21

numerical descriptive measure for a population; number that describes a population

Question 22

What are examples of population parameter?

Answer 22

population mean and variance

Question 23

What is sample statistic?

Answer 23

numerical descriptive measures for a sample; estimate of population parameter

Question 24

What is central tendency?

Answer 24

in normal distribution, values are clustered at the midpoint , thinning out systematically toward both extremes

Question 25

How do biological measurements tend to be distributed?

Answer 25

normally

Question 26

What happens as better traits are selected to the distribution?

Answer 26

mean is shifted to the right

Question 27

What are the 3 measures of central tendency?

Answer 27

Mean, Median, and Mode

Question 28

What is the median?

Answer 28

value half way between the 2 extreme values

Question 29

What is the mode?

Answer 29

class with the highest frequency

Question 30

What is the mean?

Answer 30

average of all measurements in the population (sample)

Question 31

What is the most useful statistic for estimating central tendency of most populations?

Answer 31

mean

Question 32

Formula for mean?

Answer 32

X (line over X) = ∑X

Question 33

What can mean show in terms of distribution? (?)

Answer 33

Samples from a normally distributed population may | show departure from normality

Question 34

What are the measures of distribution?

Answer 34

standard deviation, standard error, and variation (?)

Question 35

What is the measure of distribution?

Answer 35

- describes a spread, how the data varies | - deviation about the mean

Question 36

What is variance?

Answer 36

- the measure of distribution; - the average squared deviation of observations from their mean - the sum of differences between each observation and the mean in squared values

Question 37

What is the formula for variance?

Answer 37

S^2 = = ∑ (X – X (line above) )^2 | n – 1

Question 38

How is variance calculated?

Answer 38

- each observation in a population sample first has the mean subtracted from it - these deviations from the mean are FIRST squared - then squared deviations are summed - the sum of squared deviations is divided by (n-1)

Question 39

What does n-1 give?

Answer 39

a more reliable estimate of population variance

Question 40

Do limited samples account for the entire range of a population?

Answer 40

no

Question 41

Why is variance squared?

Answer 41

if not, it adds up to 0

Question 42

Is variance calculated useful?

Answer 42

yes when comparing the result to the result of another population

Question 43

What is standard deviation?

Answer 43

"typical" deviation, in absolute value, of an observation drawn at random from the population, from its mean

Question 44

What is s equal to?

Answer 44

√s^2

Question 45

What is X (line above)?

Answer 45

sample mean

Question 46

What is ∑ ?

Answer 46

sum

Question 47

What is n?

Answer 47

number of observations in a sample

Question 48

What is μ?

Answer 48

population mean

Question 49

How is standard deviation used?

Answer 49

add and subtract to mean to get a range; describe variation in a population

Question 50

What does standard deviation help us picture?

Answer 50

how much variation actually exists for a trait

Question 51

What is standard error?

Answer 51

-how accurately the mean has been estimated -If the mean were computed again from a different sample of n individuals drawn at random from the same population, how closely would the new estimate of the mean correspond to the former one?

Question 52

What is the formula for standard error?

Answer 52

S. E. = S. D. /√n

Question 53

What makes up the measure of relationships?

Answer 53

- correlation | - regression