quantitative methods
Some problems call for a quantitative solution, potentially accompanied by some qualitative research. Quantitative research provides a broad understanding of attitudes and behavior. Quantitative data allow you to generalize to the overall population, and to base decisions on reliable and representative information. Here is a list of quantitative methods.

• Telephone surveys
  For researchers, the telephone is a quick and inexpensive way to reach a representative sample of a target population. Telephone surveys are used for public–opinion polls and many other types of market research. Random-digit dialling helps ensure a representative sample of respondents. If a client is interested in a particular segment of the target population (women, for example), the calls are screened to find the right respondents. Sometimes the relevant sub-population is very small. In that case, the client provides lists of telephone numbers (of customers, for instance) or telephone numbers are purchased from database suppliers. Computer-assisted telephone interviewing (CATI) allows interviewers to work with complex questionnaires or experimental research designs.
  
  
• Mail surveys
  Mail surveys can be an inexpensive alternative to telephone surveys. They are used when:
  
  • the questionnaire is too long to be dealt with over the telephone;
    
  • it is better that respondents complete the questionnaire because of the sensitive nature of the questions;
    
  • only a small sub–population is of interest (such as customers of a particular company) and the client only has lists of addresses.
    
Because response rates can be low, a mail survey is better in a situation in which respondents are motivated to participate.


• Placed-mail surveys
  This combines many advantages of mail and telephone surveys. It is used when a mail survey is preferable, but:
  
  • a list of addresses is not available;
    
  • respondents must be screened for eligibility before participating.
  First, respondents are contacted and screened by telephone. Those willing to take part in the survey then receive a mailed questionnaire.
  

• E-mail surveys
  Where e-mail addresses are available, surveys by e-mail can be quicker and easier than mail surveys.
  
  
• On-line surveys
  On-line surveys are different from e-mail surveys in that respondents visit a central Website to complete a survey. On-line surveys are only appropriate in a situation where all, or virtually all, of the population of interest has access to the Internet or an intranet. The respondents may be recruited by telephone, an advertisement in a newspaper or, alternatively, all visitors to a Website (a company Website, for example) may be asked to complete the survey. On-line surveys can be an inexpensive way to gather data quickly. They can also be used for questionnaires involving complex question skips or experimental research designs.
  

• In-person household surveys
  In-person household surveys can be costly and time-consuming, so are used less frequently these days. They are still used:
  
  • in communities where telephone penetration remains low (such as developing countries);
    
  • in cases where the interviewer needs to show the interviewee something (a product or advertisement, for example);
    
  • where it is important that an interviewer builds a rapport with interviewees to make them feel comfortable.
  Normally, a multi-stage sampling approach is used, with random selections of houses, streets and households to help ensure a representative sample.
  
  
• Intercepts
  An intercept involves the interviewer finding respondents in an external location, such as a shopping mall or a street corner. Intercepts are used where:
  
  • telephone penetration is low;
    
  • the research involves visual or audio stimuli;
    
  • a particular sub-population is sought, no sample lists exist and the sub-population is likely to congregate in a particular location.
  To help ensure a representative sample, interviewers are required to follow careful selection procedures. Usually this involves approaching every nth passer-by. Interviewing is also conducted at specific times of the day and week to ensure no bias occurs. However, because the size and nature of the overall population are usually unknown, intercepts normally do not result in a statistically representative sample.
  
  
• Face-to-face (in-person) surveys
  Household surveys and intercepts are both examples of face-to-face surveys, which are normally used when the research involves visual or audio stimuli. They are also used in situations where a good rapport between interviewer and interviewee is important. This is often the case when interviewing decision-makers and opinion leaders such as business or political leaders.
  
  
• Recruit-to-central surveys
  Respondents may be recruited to meet at a central location for the purpose of completing a survey. This is sometimes done when:
  • the questionnaire is very complex and requires instructions, careful completion and on-going assistance (conjoint studies, for example);
    
  • the respondents are physically located near to each other (employees of a company, workers in a particular district);
    
  • the research design involves visual stimuli such as advertising;
    
  • the research design involves immediate qualitative research. In this case, respondents will be broken up into focus groups before or after completing the questionnaire.

• Diaries
  Most quantitative methods rely on respondents’ memories. When it is very important that there is a minutely accurate and detailed record, diaries can be useful. Diaries are especially important in behavioral research. For example, diaries might be used to better understand how household products are used. Questionnaires designed to record behavior and attitudes over a period of time are placed with respondents. Various incentives are used to encourage ongoing participation.