Methodology Report & Survey Data - Essay Example

Assume that the distribution is normally distributed. 2.2 In order to estimate the percentage of dwellings which have a smoke alarm in the North West to within 1% for a 95% confidence level a pilot survey was carried out. From a random sample of 30 buildings, 12 were found to have a smoke alarm installed. How many houses need to be sampled in the main survey 2.3 Two counties were surveyed by a local council in an investigation of their effectiveness in reducing the number of buildings of multiple occupancy "at risk" from arson.

The following data was obtained from the survey. Evaluation of data from each local councilTotalNumber reducingNumber remains the sameNumber increasingCounty A6253869County B314421Total9394290Expected Values6.929.932.212.19.19.8OE(O-E)(O-E)2(O-E)2/E66.9- 0.90.810.1232.10.90.810.382529.9- 4.924.010.80149.14.924.012.643831.25.833.641.0449.8-5.833.643.43Total8.41Significance = (-1)/(C-1) = (2-1)/(3-1) = 2The calculated value of 8.41 is considerably more than the significance value of 2Therefore the data represents a significant departure from the expected values thus County A shows a considerable increase in risk of arson as compared with County B and the trend is