Question

Find the standard​ deviation, s, of sample data summarized in the frequency distribution table below by using the formula​ below, where x represents the class​ midpoint, f represents the class​ frequency, and n represents the total number of sample values.​ Also, compare the computed standard deviation to the standard deviation obtained from the original list of data​ values,

11.1                

Interval

20-29

30​-39

40​-49

50​-59

60​-69

70​-79

80​- 89

	Copy to Clipboard		+
	Open in Excel		+

Frequency

22

22

22

44

17

39

29

Standard

Deviation equals=nothing

​(Round to one decimal place as​ needed.)

Consider a difference of​ 20% between two values of a standard deviation to be significant. How does this computed value compare with the given standard​ deviation,

11.1​?

A.

The computed value is not significantly different from the given value.The computed value is not significantly different from the given value.

B.

The computed value is significantly less than the given value.The computed value is significantly less than the given value.

C.

The computed value is significantly greater than the given value.The computed value is significantly greater than the given value.

7. A​ student's course grade is based on one midterm that counts as

10​%

of his final​ grade, one class project that counts as

55​%

of his final​ grade, a set of homework assignments that counts as 40​%

of his final​ grade, and a final exam that counts as

45​%

of his final grade. His midterm score is

81​,

his project score is

96​,

his homework score is

76​,

and his final exam score is

64.

What is his overall final​ score? What letter grade did he earn​ (A, B,​ C, D, or​ F)? Assume that a mean of 90 or above is an​ A, a mean of at least 80 but less than 90 is a​ B, and so on.

His overall final score is

nothing .

​(Type an integer or a decimal rounded to one decimal place as​ needed.)

His letter grade is

▼

Answer 1

Occurance(X)	Frequency(f)	Freq*X	(X-mean)	(X-mean)2	f*(X-mean)2
24.5	22	539	-32.564	1060.421	23329.257
34.5	22	759	-22.564	509.139	11201.052
44.5	22	979	-12.564	157.857	3472.847
54.5	44	2398	-2.564	6.575	289.283
64.5	17	1096.5	7.436	55.293	939.974
74.5	39	2905.5	17.436	304.011	11856.41
84.5	29	2450.5	27.436	752.728	21829.126
Total ->	195	11127.5	-	-	72917.949

Total = 24.5 x 22 + 34.5 x 22 + 44.5 x 22 + 54.5 x 44 + 64.5 x 17 + 74.5 x 39 + 84.5 x 29 = 11127.5
ΣF = 195
Mean = 11127.5/195
Mean = 57.0641

σ² = (ΣF . M² - n * µ²)/(n-1)
ΣF . M² = 22 x 24.5² + 22 x 34.5² + 22 x 44.5² + 44 x 54.5² + 17 x 64.5² + 39 x 74.5² + 29 x 84.5²
= 707898.75
σ² = (707898.75 - 195 x 57.0641²)/ 194
σ² = 375.866

σ = 19.3872

The computed value is significantly greater than the given value.

7. Wrong Question as 10%+55%+40%+45%>100%

Multiply respective values for each term and add.