variance of the mean

= np (p+q) n - 1 ..

Let X be a discrete random variable which can assume values x 1 , x 2 , x 3 ,x n with probabilities p 1 , p 2 , p 3 .. p n respectively then (a) Mean of X or expectation of X denoted by E(X) or m is given by (b) Variance of X denoted by s 2 is given ..

Find the mean, variance and standard deviation for the number of heads, when 20 coins are tossed. => 10, 5, 5 or 5, 5 2 , 5 2 or 10, 5 , 5 or 5, 5 2 , 5 2..

The number of vehicles that crossed at a traffic junction per minute at different intervals are: 120, 138, 127, 135, 132, 124, 130, 134. Find the mean and variance. => Mean = 138; Variance = 31.7 or Mean = 130; Variance = 22.3 or Mean..

The average size of a farm in one country is 200 acres and in another country it is 280 acres. If the standard deviations are 34 and 10 and sizes are 10 and 15, then find if the variances and mean sizes of each farm differ significantly at α = 0.1. => variances d..

10% of students in a school are left-handed. If 350 students are selected at random, then find the mean, variance, and standard deviation of the number of students who are left-handed. => 40, 36, 6 or 5.61, 31.5, 35 or 35, 31.5, 5.61 or 31.5, 35, 5.61..

A survey found that 54% of the people believed that Andy Roddick would win this year's US Open. If 250 people are selected at random, then find the mean and variance of the number of people who believe that Andy Roddick would win this year's US open. => 135, 7.88 or 135, 62.1 or..

The means of each group of a two-way analysis of variance for two independent variables are plotted and shown in the three graphs. Which of these represents a disordinal interaction? Consider the interaction to be significant. => Both graph 1 and graph 2 or Graph 1 or Graph 3 or..

What are the 95% and 99% confidence intervals for the population mean, if the variance is 0.64? Given that sample size = 60, sample mean = 11.21. => (11.29, 11.371) and (10.933, 11.467) or (10.997, 11.403) and (10.997, 11.403) or (11.01, 11.41) and (10.94, 11.48) or (1..

If two samples have means of 30 and 28 and variances of 12 and 14, with 20 and 25 as the sizes, find the z score for difference of two population means. => 2.154 or 2.075 or 2.320 or 1.857..