This session clarifies the concepts of P-value, alpha value, and confidence interval used in research studies as well as their relevance.

1. The Riddle of P value, Alpha Value,
and Confidence interval
Dr. Rajeev Kumar
M.S.W.,(TISS, Mumbai), M.Phil., (CIP, Ranchi) UGC-JRF., Ph.D. (IIT Kharagpur)
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Lecture-5: Research Methodology

2. Nowadays, we come across such news. But
what does these percentage actually tells us?
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3. Recap of our initial sessions
We had learnt about:
P value
Alpha value
Confidence interval.
p-value is the probability of obtaining a result. Famous statistician R. A.
Fisher, most folks typically use an alpha level of 0.05. However, if
you’re analysing airplane engine failures, you may want to lower the
probability of making a wrong decision and use a smaller alpha.
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4. Meaning of ‘P’ value and confidence interval
P value is the probability of rejecting alternative hypothesis and
accepting null hypothesis.
In other words, ‘P’ value is the chance of failure. Less the p value,
better the result.
In worldwide research, maximum accepted p value is (0.05), if we take
our number as (1).
If we consider as 100%, then it would be 5% failure.
It means we are confident of 95% success.
This 95% is called confidence interval. Lower the ‘p’ value, higher the
confidence interval, and stronger the result of statistics.
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Lower the ‘p’ value, higher the likelihood the
coverage of larger population

6. What is alpha value?
According to Statistician R. A. Fisher, the maximum accepted range of
rejecting alternative hypotheses or accepting null hypothesis or
affording the loss is 5%. Therefore we take p value as (0.05).
This minimum cut off of p value is called alpha value.
According to Fisher, our minimum success probability should be 95%.
This alpha value and confidence interval are chosen according to the
prevalent situation and the advancement of technology of that specific
period.
We can compare the alpha value with our passing marks (which are
34%) as we take p value 0.05.
But in extremely tough exam such as UPSC passing marks are less. But
in certain exams, passing marks are 50% (medical college).
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7. Types of alpha values
• We can see here, various alpha values: (.10) (0.05) (0.01) (0.001).
Now try to understand them in current examples.
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Higher the alpha value, lower generalization of
population

9. What is the confidence interval of this vaccine?
What is the p value of this vaccine trial?
What will happen, if we assess its effectiveness at
the alpha value (P≤0.05)?
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10. Which alpha value will be most appropriate for these
vaccine trials?
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11. Need to change the alpha value
If we take ά value (P≤0.05). The efficacy results of all those vaccine
trials will not be significant.
But insignificant does not mean ineffective. Here once again, we have
to realize the difference between statistical and practical significance.
All those vaccines are 90% effective, it means, their confidence interval
(CI=90%), so failure is 10%. If we take ά value (P≤0.10), all these results
will be significant.
Because amidst this extreme crisis of pandemic, when there is extreme
loss of human lives and economy, in such situation, if we could save
90% live, then it would be a great advantage. Mortality rate is already
below 3%. And we can eliminate the COVID19.
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12. In case of advanced technology
In case of modern drugs, whose effectiveness has been tested at ά
value (p≤0.05), then we will improve it further and take ά value
(p≤0.01), (p≤0.001), (p≤0.000000000000001).
In case of defence technology, we may take (p≤0.000000000001)
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13. Analyse the alpha value and confidence interval of
vaccine trial.
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14. Find out, which alpha value will be applicable
to the previous case?
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The first dose if 82% effective, it means confidence interval is 82%. If
we take ά value (P≤.20), this result will be significant.
The second dose will be 95% effective, which is universal confidence
interval (CI=95%). Here the results will be significant at (P≤0.05).

15. What do you say now about their confidence
interval, and alpha value?
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16. In different situations, we choose alpha value and
confidence interval appropriate to situations.
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17. I hope, we all have understood the riddle of p
value, alpha value, and the confidence
interval, as well as their applications in the
practical situations.
Thanks for your kind attention
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