[Ezra Halleck]

3. The distribution of grades on a quiz taken by 100 students is given in the table

(a) Compute the mean and standard deviation of this distribution. [Use definition of standard deviation (weighted sum of deviations from mean square).]
(b) Find mean & standard deviation of sample mean for random sample of size 16.

[Sunny3oy]

Where is thy table? WHERE ART THOU!

[Anonymous]

I was wondering the same about the table

[Anonymous]

I was wondering the same about the table

[Roger Herra]

should a table be created??

[Afzal]

grade number
1

---

10
2

---

40
3

---

30
4

---

20

…………………………………. this is the table/:

[yuxiaolin]

i think we can get the table on excel file, isn’t it?

[Ezra Halleck]

Afzal is right. 10 students got a grade of 1, 40 a grade of 2, 30 a grade of 3 and 20 a grade of 4. The average grade will be between 2 and 3, but not necessarily 2.5. In fact 260 divided by 100 is 2.6.

[Ziyuan Wu]

E(x)=1(.1)+2(.4)+3(.3)+4(.2)=2.6

[Jainarine Singh]

(x-u)^2 1 2 3 4
x

P(x) 1/10 4/10 3/10 2/10

[Nikoy O’Gilvie]

a) mean = 1+2+6+8/10 =2.6

b) v[x]= e[x-u)^2 = 3.30

c) sd[x]=.825

[igorekk132]

hmm for A i got
mean = 2.6
SD= 0.916

[Ezra Halleck]

x P(x) x*P(x) (x-mu)^2 (x-mu)^2*P(x)
1 0.1 0.1 2.56 0.256
2 0.4 0.8 0.36 0.144
3 0.3 0.9 0.16 0.048
4 0.2 0.8 1.96 0.392
2.6 0.84 var
0.916515139 sd

Almost, SD is 0.917.

[Richard Matos]

What is the variance 0.84?

[Richard Matos]

did anyone do part b? does the mean remain the same ?