L3: inference & estimation

Question 1

sample statistics

Answer 1

mean:x̄, var: s^2, sample prop: p

Question 2

population parameters

Answer 2

mean:μ, variance: σ^2, pop prop: π

Question 3

estimators

Answer 3

set of rules to calculate pop parameter estimate

Question 4

estimators criteria

Answer 4

bias, precision

Question 5

for higher precision

Answer 5

larger sample size (n increase = SE decrease)

Question 6

point estimate for large sample

Answer 6

sample mean

Question 7

what does 95% c.i tell you

Answer 7

95% confident that pop mean lies within 1.96 std errors of x bar (point estimate) (NOT 95% prob)

Question 8

what does z val (e.g. 1.96) tell you at 95% c.i.

Answer 8

95% of data estimates is +/- 1.96 s.d. of mean (within 2.5 tail)

Question 9

how does confidence level capture uncertainty

Answer 9

estimate drawn from sample (diff sample = higher / lower estimate)

Question 10

smaller sample size on CL

Answer 10

wider - greater uncertainty

Question 11

99% confidence interval on table

Answer 11

0.5% each tail = 0.005 on z table (=2.575)

Question 12

sample proportion mean and variance

Answer 12

mean: 𝜋, variance: 𝜋(1-𝜋) / n

Question 13

sample proportion distribution

Answer 13

p~N(𝜋, [𝜋(1-𝜋)]/n)

Question 14

confidence level for sample proportion

Answer 14

same as mean; p +/- interval est √[𝜋(1-𝜋)]/n)

Question 15

point estimate for sample proportion

Answer 15

p (=𝜋 bc 𝜋 unknown)

Question 16

t distr used when

Answer 16

n is small, 𝝈 unknown

Question 17

degrees of freedom

Answer 17

v=n-1

Question 19

for d distr, 2 things you need to knwo

Answer 19

v=n-1, ⍺/2= area in each tail