أسئلة أحصـــــــــــــــــــاء =)

[b7bk oo]

مرحبااا
أنا عجزت في حل هدي الأسئله بليز ساعوني في حللها
اعتبرووه كأنوا مراجعه لكم كلل وحد تحل إلي تعرفه بلييز

If P(a<z<b)=0.95, then the value of the standard deviations equals

A) 2

B) 3

C) 0.05

D) 1

23. The average height of Apple trees in a garden is 10.5 feets. If the heights are normally distributed with a standard deviation of 3, find the percentage that a tree is less than 12.5 feets tall

A) 74.86%

B) 24.86%

C) 66.67%

D) 25.14%

25. The average weight of books on a library f is 8.3 grams. The standard deviation is 0.6 grams. If 20% of the books are oversized , find the minimum weight of the large books on the library f. Assume the variable is normally distributed.

A) 8.612 grams

B) 0.3 gram

C) 0.84 gram

D) 8.804 grams

The coefficient of variation of the height of 20 people selected at random from a given city is found to be 16%. The weight of the selected group has a mean value 72 kg and a standard deviation 6 kg.

6. The coefficient of variation for the weight of the selected group is ...

A) 11.11% B) 8.33% C) 11.11 D) 8.33

7. The obtained results show that ...

A) the weight is less variable than height.

B) height and weight are independent.

C) the weight is more variable than height.

D) height and weight have the same degree of variation

36. If the standard deviation of a population is 84 and we took a sample of size 32, then the standard error of the mean (the standard deviation of the sample mean) is ...

A) 14.849 B) 11.685 C) 8.485 D) 8.398

6. A survey found that the microwave ovens have an average life of 3 years with in a standard deviations of 0,5 years. Assume the variable is normally distributed . what percent of microwave ovens would be replaced if 18 months were given ?

0,13%

11. A survey found that the microwave ovens have an average life of 2 years with a standard deviation

of 0.5 year. Assume the variable is normally distributed. What percent of microwave ovens would

be replaced if a warranty of 21 months were given?

A) 6.68% B) 30.85% C) 93.32% D) 69.15%

The monthly income, X, of a family in a given city is normally distributed with mean $1666 and standard

deviation $674.

12. The standard error of the mean for a random sample of size 34 is ...

A) 121.328 B) 115.590 C) 117.328 D) 123.055