ECON 221 Study Guide - Midterm Guide: Frequency Distribution, Asteroid Family, High Tech
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1. thirty aa batteries were tested to determine how long they would last. The results, to the nearest minute, were recorded as follows: 372, 410, 419, 386, 390 (a) note that the lowest value is 363 and the highest is 431. Construct a frequency distribution, involving 8 class intervals, starting with 360-369 (range of battery life in minutes). Call the mid-value of the ith class as. Xi and its frequency as (fi); i=1,2, 8. comment on the shape of the histogram (symmetric or asymmetric). (b) find the relative frequency of each class (pi = fi /n; n=30) and the probability distribution of x. Comment: both are the same and slightly skewed to the right. (c) find e(x) and var. (x). E(x)= 397. 5 var. (x)=327. 29 x= 18. 091 (d) let y= 363+ 2x. 3: it seems that a large number of high-tech positions are being filled by younger employees.
