Answer
$5.3 \%$ of those who minimised or decreased their spending on music were experienced files sharers with broadband access.
Work Step by Step
According to Bayes' theorem:
$P(E|D)=\dfrac{P(D|E)P(E)}{P(D|E)P(E)+P(D|E')+P(E')}~~~~~~~~(1)$
Here, we have
$P(D|E)= 36 \% =0.36\\ P(E)= 3 \% =0.03 \\ P(D|E')=20 \% =0.2$
Now, we will now use formula (1) and the given data to obtain:
$P(I|D)=\dfrac{P(D|I)P(I)}{P(D|I)P(I)+P(D|I')+P(I')}=\dfrac{(0.36)(0.03)}{(0.36)(0.03)+(0.2) (1-0.03)}$
or, $=0.053$
or, $=5.3 \%$
Thus, we conclude that $5.3 \%$ of those who minimized or decreased their spending on music were experienced files sharers with broadband access.
