Question

From the analysis of rainfall data at a particular station, it was found that a rainfall of 400 mm had a return period of 20 years. What is the probability of rainfall equal to or greater than 400 mm occurring atleast once in 10 successive years?

• A. $(0.95{)}^{10}$
• B. $1-(0.95{)}^{10}$
• C. $1-(0.05{)}^{10}$
• D. $(0.05{)}^{10}$

Answer 1

The correct option is B $1-(0.95{)}^{10}$

The probability of occurrence of an event at least once over a period of 'n' successive years is called the risk, R. It is given as
$R=1-(1-P{)}^n$
$whereP=\frac{1}{T}=\frac{1}{20}=0.05$
$\therefore R=1-(1-0.05{)}^{10}$
$=1-(0.95{)}^{10}$