Section Progress:

Where to Conduct Your Survey

An observational site for conducting your survey should be neutral and non-disruptive, yet allow for comfortable discussions. Native CARS found that the best place to ask people to participate in your survey is in the parking lots of:

  • Grocery stores
  • Gas stations
  • Trading posts
  • Schools/preschools
  • Tribal Clinic
  • Tribal events & celebrations

Places such as the community center, health clinic, gas station, trading post, grocery store, elementary school, preschool, or Head Start are all good locations to conduct surveys.We found trading posts, grocery stores and gas stations to be ideal sites. People at these places were less likely to be in a hurry, there was a more continuous flow of vehicles entering and leaving the site, and outside of school hours, children of all ages were equally likely to be found there.The parking lot is a neutral location, and speaking to people in the parking lot won’t disrupt the business or organization.  Make a list of all potential observation sites and attempt to collect data at each location. Contact the business or agency before you visit to make sure you have permission to do surveys in their parking lot. Most schools require observers to sign in at the office and identify themselves with a volunteer badge. Be sure to respect the policies of the organizations you are visiting. The surveys are done in parking lots when cars are stopped, either as a vehicle first pulls in, or right before the vehicle departs. In our experience, very few locations denied permission.  You will want to limit the number of surveys collected at preschools and elementary schools to less than 40% of your total sample to avoid having too many surveys of a specific age group of children. So, if you do 100 surveys, make sure 60 of them come from places other than preschools and schools.

When to Do the Survey

Spring and fall are the best times. For the safety of data collectors, the surveys should be conducted only during daylight hours. Since there is an observation element to the survey, if it is dark outside, it will be too dark to see how the child is restrained in the vehicle. Since the surveys are conducted outside, winter might not be the most feasible time for the survey. Spring and fall are good times for the survey because the weather can be milder and schools are in session.  If you conduct the survey during the summer, keep in mind that there are seasonal differences in how people travel, especially when school is not in session.  Whenever you choose to do your survey, it is best to repeat the survey during the same season in the future to obtain a reliable comparison over time.

How Many Observational Interviews to Complete

Collecting information on 100 children will give you useful data. If you want more statistical precision, read on.

Your sample size depends on the size of your population and the proportion of children who are properly restrained. Here are a few steps to help you determine your sample size.

1.       Define your population

Native CARS used “Children age 8 & younger traveling in tribal communities.” You could choose to collect data on Native children only. Or clinic users. Look at your list of potential observation sites and think of the children you might observe there.  Also, think of who you are trying to reach with your intervention activities. This will help you define your population.

 2.       Estimate how many people are in your population

Tribal enrollment numbers, census data for your area, or clinic user population can help you with a ballpark estimate.  If you do not know the population of children in the area, but do know the entire community population, you can estimate that children age 8 and younger make up 17% of the total population in the average American Indian community, according to the U.S. Census. https://factfinder.census.gov/faces/nav/jsf/pages/index.xhtml

 3.       Estimate the proportion who are properly restrained

You are probably thinking, “If I already knew this, I wouldn’t be doing this survey!”  But for the calculator, we need to make a guess. The most conservative (safest) guess is 50%. The farther you get from 50%, in either direction, the fewer observations you need to do to get a valid estimate. So, if you really have no idea, pick 50%.

The sample size table below will tell you how many children you need to observe to estimate the proportion of children who are meeting restraint recommendations with 5% precision (margin of error) and a 95% confidence level. If your population is somewhere between these numbers, your sample size will be too. For example, if your population has 300 children age 8 & younger, and you think half of them are properly restrained, look at the sample size for a population of 250 (152) and do a few more than that, say 170. Alternatively, you can use the web calculators below to get specific estimates for your population.

Keep in mind that your sample size is the number of children to observe. You will likely see multiple children in one vehicle. You will reach your goal numbers faster than you might think.

 

Number of Children to Observe for an Estimate with a 5% Margin of Error and 95% Confidence Level

Estimated proportion of properly restrained children Number of children age 8 or younger in the community
100 250 500 1000 1500 2000
30% 77 141 197 245 266 279
40% 79 150 213 270 297 312
50% 80 152 218 278 307 323
60% 79 150 213 270 297 312
70% 77 141 197 245 266 279
80% 72 124 165 198 212 220
90% 59 90 109 123 128 130

 

http://epitools.ausvet.com.au/content.php?page=1Proportion&Proportion=0.5&Conf=0.95&Precision=0.05&Population=1000

http://sampsize.sourceforge.net/iface/

For information on who to interview, and guidance on conducting interviews, go to the next section.