Math Tools for Journalists Chapter 5-8

By Stuart Jones

Polls and Surveys Chapter 5

Polls and surveys offer only a glimpse of public opinion, and often are skewed one way or another. It is the reporter’s job to help readers understand the validity of polls and surveys they are reading about. Polls are an estimate of public opinion on a single topic or question. Random selection is an essential part of polling, because without the results can become biased.

  • A valid sample is large enough to represent the population under study.
  • Census or population sampling involves sampling everyone in the population.
  • Margin of error indicates the degree of accuracy of the research based on standard norms. It is expressed as a percentage and is based on the size of a randomly selected sample. The margin of error should be included in all stories related to polling.
  • Confidence level is the level or percentage at which researchers have confidence in the results of their research.
  • Z scores and t scores.
    • Z score (standard score) shows how much a particular figure differs from the mean. The standard deviation is used as the unit measure. The mean becomes zero and the first standard deviation is 1, the second is 2 and so on. Z scores can be negative or positive according to their relation to the mean
    • T scores (Student’s t distribution) is used when the sample size is roughly 100 or fewer.
    • Z score = (raw score – mean) / standard deviation

Business Chapter 6

  • Financial statements can help a reporter understand how the business is doing as well as where it might be projected to go from there.

Profit and Loss

  • This statement shows whether a company is making money or not. This includes a breakdown of different expenses and gross profit.

Gross margin = selling price – cost of goods sold

Gross profit = gross margin x number of items sold

Net profit = gross margin – overhead

Balance Sheet

  • A financially written statement of a company’s assets, liabilities and equity. It is often an indicator of the company’s financial stability.

Assets = liabilities + equity

  • Assets- resources owned by a company that have some economic value

Ratio Analysis

  • Ratios are calculations that analysts and business owners use to evaluate a company’s cash situation, profitability, operating efficiency and market value.
  • Current ratio = current assets/current liabilities

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