Download NotesCh.7(12th.Ed)

Ch. 7 Estimating population parameters and finding minimum sample size needed to estimate …
Recall from ch. 6 with sampling distributions that the sample proportions , means and variances are
good, unbiased estimators of the population proportions , means and variances. Note the distribution
of sample proportions and sample means is normally distributed but the distribution for variances is
skewed to the right (most data on left with very little data on the right). See page 275 in textbook.
Section 2: Estimating population proportions (percentages)
POINT vs. INTERVAL estimates (page 324-5)
Correct INTERPRETATION of confidence intervals (pages 326-7)
Confidence level (middle part of curve), level of significance (α – the left over and put half in each tail)
and critical values (see pages 326)
Margin of Error definition and formula (page 329)
Symbols, formulas and requirements for confidence interval estimates (CIE) for population proportions
(page 330)
Round off rule for confidence interval estimates (CIE) of population proportions (page 330)
Determining sample size required to estimate a population proportion (page 333)
Round off rule for sample size (page 333)
see video for examples from 11th edition p. 341 #32 and p. 343 #42 (see other handout)
Section 3: Estimating population means
POINT vs. INTERVAL estimates (page 343)
Symbols, formulas and requirements for confidence interval estimates (CIE) for population means (page
344 and 353)
Degrees of freedom and finding t critical values from Table A-3 in your book (page 348)
Important properties of a Student t distribution (page 348)
Choosing the appropriate distribution (pages 354)
Round off rules for confidence interval estimates (CIE) of population means (page 344)
Correct INTERPRETATION of confidence intervals (pages 346)
Determining sample size required to estimate a population mean (page 351-2)
NOTE: Remember we must have an normal distribution with original data OR a sample size that is large
enough (n >30) in order to use the CLT.
see video for examples from 11th edition p. 353 #26 and p. 354 #34 (previously section 7.3)
See video for examples from 11th edition p.367 #22 and p. 365 #6,8,10,12 (previously section 7.4)
Section 4: Estimating population standard deviations and variances
Chi-square distribution (page 361-2) and Table A-4 for Chi-square critical values
POINT vs. INTERVAL estimates of variance and standard deviation (page 361-2)
Symbols, formulas and requirements for confidence interval estimates (CIE) for population variances
and population standard deviations(pages 364-5)
Round off rules for confidence interval estimates (CIE) of population variances and population standard
deviations - same as for estimating population means (page 364)
Determining sample size required to estimate a population variances and population standard
deviations (page 367)
See video for example from 11th edition p. 379 #20 (previously section 7.5)
What population parameter are
estimating with a confidence
interval?
Population
proportion/rate/percentage
Find the sample proportion (𝑝̂ ) which
is the point estimate.
Add and subtract margin of error to
create interval.
p̂ ± E where E =
z
2
pˆ qˆ
n
Population mean
Assumption: Original population
must be normally distributed OR
sample size is large enough (n >
30) in order to use either the t or
z distribution.
Formula: x ± E
where E =
z 
2
n
or E =
t s
2
n
Population standard deviation or
variance Find the sample standard
deviation or variance.

 (n  1) s 2 (n  1) s 2
,

2
2
 

R
L



2
 for σ

