In: Statistics and Probability
Admissions to the emergency department have been grouped by time of admission and patient problem. Counts for the last week are as follows:
Day | Evening | Night | Total | |
Minor injury | 125 | 60 | 20 | 205 |
Abdominal pain | 130 | 120 | 80 | 330 |
Other | 210 | 170 | 140 | 520 |
Total | 465 | 350 | 240 | 1055 |
A) What proportion of admissions are in the evening?
B) What proportion of admissions are in the evening and minor injuries?
C) What proportion of admissions are in the evening or minor injuries?
D) Among the admissions in the evening, what proportion are for minor injuries?
E) If the admission was for a minor injury, what proportion are in the evening?
F) Are “evening admission” and “minor injury” independent events? Use probability to justify the answer.
We will be looking at the first 4 parts here:
a) The proportion of admissions that happen in the evening is
computed here as:
= Total admissions in evening / Total number of admissions
= 350 / 1055
= 0.3318
Therefore 0.3318 is the required proportion here.
b) The proportion of admissions that are in the evening and
minor injuries is computed here as:
= Total admissions in evening and minor injuries / Total number of
admissions
= 60/1055
= 0.0569
Therefore 0.0569 is the required probability here.
c) The proportion of admissions are in the evening or minor injuries is computed using law of addition as:
P( evening ) + P(minor injuries ) - P(evening and minor injuries)
= (350 + 205 - 60) / 1055
= 0.4692
Therefore 0.4692 is the required proportion here.
d) Among the admissions in evening, proportion of minor injuries here are computed using Bayes theorem as:
P(minor injuries | evening) = P(minor injuries and evening) / P(evening)
= 60/350
= 0.1714
Therefore 0.1714 is the required probability here.