Characterizing Top 5% of Influent Substrate Concentration in Reactor

[needhelp83]

Substrate concentration (mg/cm^3) of influent to a reactor is normally distributed with $$\mu = 0.30$$ and $$\sigma$$ = .06

The question is how would you characterize the largest 5% of all concentration values?

What does this mean?

 

[Fightfish]

I think its probably P(X>=k) = 0.05, solve for k.

 

[needhelp83]

I think its probably P(X>=k) = 0.05, solve for k.

P(X >= k) =0.05
1- n = 0.05 n= 0.95 (Look up value in z-table)
1.64 = 0.9495

$$\frac{k - 0.30}{0.06}=0.9495$$

After solving, k = 0.36