normal distribution and estimation

Question 1

differences for symmetric and asymmetric quantitative data

Answer 1

symmetric use mean and SD (bell shaped ND)

asymmetric use median min/max and Q1 and Q3

Question 2

what is the sample and the population

Answer 2

sample is the data we use

pop. is theoretical group of all people we could have sampled (and from where the sample came from)

Question 3

most samples bias but try remain representative

Answer 3

random sample is where each member of pop. has equal chance of being selected

Question 4

subjective inference

Answer 4

using data from sample we can infer qualities for the pop. as a whole

Question 5

N(u, o^2)

Answer 5

u-mean
o-SD
o^2 - variance
n(not N) - number in sample

Question 6

check normality

Answer 6

symmetric box-lot, mean roughly equals median

mean+- 2 SD contains most of data

Question 7

SD of sample means is known as the standard error

Answer 7

SE=pop.SD/(square root of n)

estimated SE uses sample SD

Question 8

what is the SD

Answer 8

measure of variability of data

Question 9

confidence interval

Answer 9

how well population mean is estimated

Question 10

95% of sample means are +- 1.96 SE of population mean

Answer 10

so if sample mean (xbar) is within +-1.96SE of population mean then sample mean (xbar)+-1.96SE contains population mean(u)

Question 11

95%confidence interval

Answer 11

will contain pop.mean with 95% confidence

Question 12

confidence interval assumes large sample

Answer 12

> 30