The frequency distribution below shows the distribution for suspended solid concentration(in ppm) in river water of 50 different waters collected in September 2011.
|
Concentration (ppm)
|
Frequency
|
|
20 - 29
|
1
|
|
30 - 39
|
8
|
|
40 - 49
|
8
|
|
50 - 59
|
10
|
|
60 - 69
|
12
|
|
70 - 79
|
7
|
|
80 - 89
|
2
|
|
90 - 99
|
2
|
1. What percentage of the rivershad suspended solid concentration greater thanor equal to 70?
2. Calculate the mean of this frequency distribution.
3. In what class interval must the median lie? Explain your answer.(You don't have to find the median)
4. Assume that the smallest observation in this dataset is 20. Suppose this observation were incorrectly recorded as 2 instead of 20. Will the mean increase, decrease, or remain the same? Will the median increase, decrease or remain the same? Explain your answers.
Refer to the following information for Questions 5 and 6.
A coin is tossed 4 times. Let A be the event that the first toss is heads. Let B be the event that the third toss is heads.
5. What is the probability that the third toss is heads, given that the first toss is heads?
6. Are A and B independent? Why or why not?