1. The data is catergorical since it is split into culture confirmed matching A or B. Any culture flu A
or B, ad any culture or serology confirmed influenza A or B.
Quantitative Variable
A quantitative variable is naturally measured as a number for which meaningful
arithmetic operations make sense. Examples: Height, age, crop yield, GPA, salary,
temperature, area, air pollution index (measured in parts per million), etc.
Categorical Variable
Any variable that is not quantitative is categorical. Categorical variables take a value that
is one of several possible categories. As naturally measured, categorical variables have no
numerical meaning. Examples: Hair color, gender, field of study, college attended,
political affiliation, status of disease infection.
2. Take the overall data from VMCCI and the overall data from teh vaccine/placebo. Do a t test.
The t-test assesses whether the means of two groups are statistically different from each other.
This analysis is appropriate whenever you want to compare the means of two groups. Compare
the placebo the control to the vaccine group to the number of affected.
a. T-test
b. One-sided since only care about how far the control (the placebo) is from the vaccine. In
testing this drug, you are only interested in testing if it more effective than the placebo.
Null hypothesis: There is no difference in VVMCCI cultures between the placebo or the
vaccine shot. Alternative Hypothesis: There is a significant difference between the
VMCCI cultures between those who received the placebo or the vaccine
3. Unpaired t test results
P value and statistical significance:
The two-tailed P value is less than 0.0001
By conventional criteria, this difference is considered to be extremely statistically
significant.
Confidence interval:
The mean of Vaccine minus Placebo equals -22.000
95% confidence interval of this difference: From -22.704 to -21.296
Intermediate values used in calculations:
t = 61.3845
df = 7480
standard error of difference = 0.358
Learn more:
GraphPad's web site includes portions of the manual for GraphPad Prism that can help you
learn statistics. First, review the meaning of P values and confidence intervals. Then learn
how to interpret results from an unpaired or paired t test. These links include GraphPad's
popular analysis checklists.
Review your data:
Group
Vaccine
Placebo
Mean
23.000
45.000
SD
15.500
15.500
SEM
0.254
0.253
N
3714
3768
The null hypothesis is rejected the placebo and vaccine group are significantly different.
5.
6. Type I error is the incorrect rejection of a true null hypothesis. It is a false positive. This would be
that the fact that the difference we found between the placebo and the drug group actually
does not exist and the vaccine actually does not help. Type II is the failure to reject a false null
hypothesis. It is a false negative. This would be if we did not find a significance difference
between the placebo and the vaccine, but there is. Either way these errors would not be good
for the general public.
7. 0.014331
8. P value more convincing. A high efficacy does not suggest a high difference in the rates of flu. It
is the p value and SD it is small bc it is saying that 95% sure that the vaccine actually works. The
.05 p is saying that there is a 5% chance you cannot reject the null.
9. Yes this vaccine protects against the flu. I am 99.9% sure that the null hypothesis is rejected
according to the t-test, therefore there is a significant difference between those who receive the
shot and get the flu and those who do not receive the flu shot and get the flu.
10. Use a t-test again.Null hypothesis there is no difference between LCI groups who recieved or did
not recieve the vaccine. Alternative: There is a difference in LCI between people who recieved
the vaccine or did not recieve the vaccine
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3. Enter data
4. View results
Unpaired t test results
P value and statistical significance:
The two-tailed P value is less than 0.0001
By conventional criteria, this difference is considered to be extremely statistically
significant.
Confidence interval:
The mean of Vaccine minus Placebo equals -78.0000
95% confidence interval of this difference: From -80.5050 to -75.4950
Intermediate values used in calculations:
t = 61.1780
df = 7480
standard error of difference = 1.275
Learn more:
GraphPad's web site includes portions of the manual for GraphPad Prism that can help you
learn statistics. First, review the meaning of P values and confidence intervals. Then learn
how to interpret results from an unpaired or paired t test. These links include GraphPad's
popular analysis checklists.
Review your data:
Group
Vaccine
Placebo
Mean
44.0000
122.0000
SD
55.1400
55.1400
SEM
0.9048
0.8983
N
3714
3768
a. P value less than p<.05 in fact p<.001 like in 3
b. Since LCI confirms the flu and the p is significant meaning there is a difference between
people who receive the vaccine and the placebo and their LCI so not does not
overestimate.