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A company which produces batteries claims that the life expectancy of their batteries is 90 hours. In order to test the claim, a consumer interest group tested a random sample of 40 batteries. The test resulted to a mean lif expectancy of 87 hours. Usoing a 0.05 level of significance, can it concluded that the life expectancy of their batteries is less than 90 hours? Assume that the population standard deviation is known to be 10 hours.
A politician wants to know his chances of winning in the next election. He has tasked a researcher to interview a random sample of his contituents about their perceptions of his leadership. Previous polls have revealed that approximately 62.5% are in favor of his leadership. The politician has adopted the 90% confidence level and of the population value by at most 0.02. How many respondents must be interviewed?
A bottle of juice drink is claimed to be 500 mL with standard deviation of 20 mL. Ramil wants to investigate the same fruit juice drink to estimate the true population mean content correct to within 5mL, adopting a 95% confidence. How many bottles of the fruit juice drink of the same brand does he need for a sample?
The age of the population in Wakanda is shown in the following table in the form of a grouped frequency distribution.
Age (years)
Number (‘000)
0 Under 5
5 under 15 15 under 30 30 under 50 50 under 65 65 under 80 80 under 100
Total
Use the data in the table above to estimate for of population in Wakanda the:
1 375.3 2 750.5 4 514.7 6 137.7 3 821.7 2 045.7 783.2
100 under 110
what is the median age?
A and B manufacture two types of cables, having mean breaking strengths
of 4000 and 4500 lb and standard deviations of 300 and 200 lb,
respectively. If 100 cables of brand A and 50 cables of brand B are tested,
what is the probability that the mean breaking strength of B will be (a) at
least 600 lb more than A, (b) at least 450 lb more than A?
For a segment of a radio show, a disc jockey can play 10 records. If there are 14 records to select from, in how many ways can the program for this segment be arranged?
Given there is 0.85 probability that any given adult knows Twitter, find the probability of getting four adults who know of Twitter when seven adults are randomly selected.
A university's leadership council is made up of 14
members: 5
are students, 4
are teachers, and 5
are deans. A newspaper reporter is planning to select two of the council members for interviews. The first member will be chosen at random, and then the second member will be chosen at random from the remaining members. What is the probability that two teachers will be selected?
A box of 10 items, 2 are defective. Items are randomly selected from the box one by one and examined. What is the probability that the sixth item selected is the last defective
In a lottery. Players must match five numbers plus a bonus number. White balls are chosen from 59 white balls numbers from 1 to 59,and one red ball(the bonus number) is chosen from 35 red balls numbered 1 to 35. How many different results are possible?
