WPC 300 FINAL EXAM WITH COMPLETE
SOLUTIONS GRADED A+
Typical sampling mistake - Answer- -Unrepresentative sample
-Biased respondents
-Low response rate (non-response bias) or lower sample size
-Biased questions
Online Survey - Answer- Polls are completed only by visitors to the site
-Those with an interest in the website's mission are the only ones who will participate
Non-response - Answer- -Some individuals are less likely to respond to a survey, e.g.,
want their opinion about smoking weed
Social Desirability - Answer- -Want to study what factors lead to academic dishonesty
-Who will be participating?
Observation: - Answer- Expected mean of the sample means is the true population
mean
-The standard deviation of sample mean distribution (SE) decreases as the sample size
"n" increases
-Increasing sample size "n" reduces the average sampling error
confidence interval - Answer- -is a range of values that is likely to contain the population
mean
confidence level - Answer- - is the proportion of samples that will yield a confidence
interval that actually contains
the population means.
Z-statistics - Answer- is good for larger sample (n>30) with underlying distribution of the
population may or
may not be normal
T-statistics - Answer- - is used when population SD is unknown
Testing the hypothesis - Answer- -When p-value is lower than α, then reject the null
hypothesis
Confidence Level - Answer- If CL = 98%, the confidence interval gets wider than when
CL = 95%.
-You do so to be more confident in your results.
, Sample Size - Answer- -If you increase the sample size, the CI becomes narrower
-You get more precise measurement
Standard Deviation - Answer- -If you increase your SD, the confidence interval gets
wider
-Your have more uncertainty and less precision in your measurement
Anova - Answer- Useful when you are comparing more than two sample means
-Observations are independent Equal variances for each population
-This process investigates variances to establish if the means are significantly different
Bonferroni - Answer- extremely general and simple, but often not powerful
Tukey's - Answer- the best for all-possible pairwise comparisons when sample sizes are
unequal or confidence intervals are needed; very good even with equal samples sizes
without confidence intervals
-Stepdown - Answer- -the most powerful for all possible pairwise comparisons when
sample sizes are equal
Dunnett's - Answer- -for comparing one sample ("control") to each of the others, but not
comparing the others
to each other.
Correlations - Answer- -When variables are correlated, it means they vary together
-Correlation can be positive, negative or zero.
Descriptive Statistics - Answer- -Shows the strength of a relationship
How reliable is conclusion - Answer- You can infer/conclude about the population with a
certain confidence level. (You will be
able to find out if the claim is really correct or not with certain confidence level - 95%)
Random sampling - Answer- is a part of the sampling technique in which each sample
has an equal probability of
being chosen
-meant to be an unbiased representation of the total population.
Inferential Statistics - Answer- -Allows to make decision about a parameter in the
population
-You want to know if the population correlation is different from zero?
- Ho = There is no significant correlation between the variables, r=0
-Ha = Null hypothesis is not true
SOLUTIONS GRADED A+
Typical sampling mistake - Answer- -Unrepresentative sample
-Biased respondents
-Low response rate (non-response bias) or lower sample size
-Biased questions
Online Survey - Answer- Polls are completed only by visitors to the site
-Those with an interest in the website's mission are the only ones who will participate
Non-response - Answer- -Some individuals are less likely to respond to a survey, e.g.,
want their opinion about smoking weed
Social Desirability - Answer- -Want to study what factors lead to academic dishonesty
-Who will be participating?
Observation: - Answer- Expected mean of the sample means is the true population
mean
-The standard deviation of sample mean distribution (SE) decreases as the sample size
"n" increases
-Increasing sample size "n" reduces the average sampling error
confidence interval - Answer- -is a range of values that is likely to contain the population
mean
confidence level - Answer- - is the proportion of samples that will yield a confidence
interval that actually contains
the population means.
Z-statistics - Answer- is good for larger sample (n>30) with underlying distribution of the
population may or
may not be normal
T-statistics - Answer- - is used when population SD is unknown
Testing the hypothesis - Answer- -When p-value is lower than α, then reject the null
hypothesis
Confidence Level - Answer- If CL = 98%, the confidence interval gets wider than when
CL = 95%.
-You do so to be more confident in your results.
, Sample Size - Answer- -If you increase the sample size, the CI becomes narrower
-You get more precise measurement
Standard Deviation - Answer- -If you increase your SD, the confidence interval gets
wider
-Your have more uncertainty and less precision in your measurement
Anova - Answer- Useful when you are comparing more than two sample means
-Observations are independent Equal variances for each population
-This process investigates variances to establish if the means are significantly different
Bonferroni - Answer- extremely general and simple, but often not powerful
Tukey's - Answer- the best for all-possible pairwise comparisons when sample sizes are
unequal or confidence intervals are needed; very good even with equal samples sizes
without confidence intervals
-Stepdown - Answer- -the most powerful for all possible pairwise comparisons when
sample sizes are equal
Dunnett's - Answer- -for comparing one sample ("control") to each of the others, but not
comparing the others
to each other.
Correlations - Answer- -When variables are correlated, it means they vary together
-Correlation can be positive, negative or zero.
Descriptive Statistics - Answer- -Shows the strength of a relationship
How reliable is conclusion - Answer- You can infer/conclude about the population with a
certain confidence level. (You will be
able to find out if the claim is really correct or not with certain confidence level - 95%)
Random sampling - Answer- is a part of the sampling technique in which each sample
has an equal probability of
being chosen
-meant to be an unbiased representation of the total population.
Inferential Statistics - Answer- -Allows to make decision about a parameter in the
population
-You want to know if the population correlation is different from zero?
- Ho = There is no significant correlation between the variables, r=0
-Ha = Null hypothesis is not true
