1 Research was conducted regarding in app purchases associat

1. Research was conducted regarding \"in app\" purchases associated with online games like Candy Crush and Clash of Clans. The research showed that 73.2% of gamers spent an average of $8.22 on \"in app\" purchases associated with a game in the previous 30 days. The expenditures were approximately normally distributed with a standard deviation of $1.10. Based on this information, 80% of the gamers spent more than what amount on \"in app\" purchases?

Solution

Normal Distribution
Mean ( u ) =8.22
Standard Deviation ( sd )=1.1
Normal Distribution = Z= X- u / sd ~ N(0,1)                  
P ( Z > x ) = 0.8
Value of z to the cumulative probability of 0.8 from normal table is -0.84
P( x-u/ (s.d) > x - 8.22/1.1) = 0.8
That is, ( x - 8.22/1.1) = -0.84
--> x = -0.84 * 1.1+8.22 = 7.2938                  

80% of the gamers spent $7.294 amount on \"in app\" purchases