STAT 250 Probability
posted by Jane Segurra .
Final averages are typically approximately normally distributed with a mean of 66 and a standard deviation of 10.5. Your professor says that the top 5% of the class will receive an A; the next 15%, a B; the next 47%, a C; the next 22%, a D; and the bottom 11%, an F.
(a) What average must you exceed to obtain an A?
(b) What average must you exceed to receive a grade of C or better?
(c) What average must you obtain to pass the course? (You'll need a D or better.)

I will let you play with
http://davidmlane.com/normal.html
click on "value from an area" and enter
mean: 66
sd: 10.5
click on below and enter .95 in area
I get 83.275
So 95% of the students will have a score of less than 83
the next 15 % will get a B
so 20 % will get either A or B
and 80% will not get A or B
click on below and enter .8 in area
I got 74.835 or 75% to 83 will get you a B
67% will get at least a C
enter .67 in area to get 70.615
I will let you continue
Respond to this Question
Similar Questions

Statistics 250
Final averages are typically approximately normally distributed with a mean of 65 and a standard deviation of 8. Your professor says that the top 10% of the class will receive an A; the next 20%, a B; the next 41%, a C; the next 19%, … 
Statistic
Final averages are typically approximately normally distributed with a mean of 78 and a standard deviation of 11. Your professor says that the top 6% of the class will receive an A; the next 24%, a B; the next 41%, a C; the next 18%, … 
STAT 250 Probability
Final averages are typically approximately normally distributed with a mean of 66 and a standard deviation of 10.5. Your professor says that the top 5% of the class will receive an A; the next 15%, a B; the next 47%, a C; the next … 
Statisitics
In a large section of a Chemistry class, the points for the final exam are normally distributed, with a mean of 72, and a variance of 81. Grades are to be assigned according to the following rule: the top 10% receive As, the next 20% … 
STAT
The score on a test are normally distributed with a mean of 75 and a standard deviation of 6. If the professor wishes to give A’s to the top 4%, what would be the cutoff score be for A’s? 
statistics
Professor Smith gave a final exam in her history class. The scores on the final exam are normally distributed with a mean of 75 and a standard deviation of 6. If Professor Smith wishes to give A’s to the top 4%, what would be the … 
STATS HELP
Final averages are typically approximately normally distributed with a mean of 72 and a standard deviation of 12.5. Your professor says that the top 8% of the class will receive an A, the next 20% a B, the next 42% a C, the next 18% … 
Math
In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of 72 and a standard deviation of 9. Grades are to be assigned according to the following rule: The top 10% receive A's. … 
Math
In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of 72 and a standard deviation of 9. Grades are to be assigned according to the following rule: The top 10% receive A's. … 
Stats
In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of 72 and a standard deviation of 9. Grades are to be assigned according to the following rule: The top 10% receive A's. …