Sample Size Needs

07/25/24 • 27 min

Shifting focus to sample size determination, Matt, Grant, and Randy explore the challenges and considerations in choosing appropriate sample sizes for reliable ecological research. They discuss trade-offs, budget constraints, and introduce the concept of power analysis for enhancing the reliability of ecological studies.

Quotes from this episode:

"In this podcast, we're going to talk about sample size needs. How many samples does a person need to collect to get a representative sample of the population? So it leads us back to this whole representativeness idea. If a person samples too few, then there's a very good chance that person is going to include a disproportionate number of outliers, oddballs or anomalies in the sample."

"...in the earlier episode we said, if all the plants have the same number of tomatoes we would just have to sample one of them. That was an invariant population. But we also spoke to that some plants had 100 tomatoes and some had none. And so we have extreme variability."

"... (the amount) of uncertainty you're willing to deal with, and how much imprecision you're willing to deal with really drives your sample

size needs....You've got to take both of those things into consideration. How variable is my population and then how certain do I want to be? How much error am I willing to accept in my final estimate?"

Episode music: Shapeshifter by Mr Smith is licensed under a Attribution 4.0 International License. https://creativecommons.org/licenses/by/4.0/

https://freemusicarchive.org/music/mr-smith/studio-city/shapeshifter/

Cite this episode: https://doi.org/10.7944/usfws.wbtn.s01ep03

Citation formatter: https://citation.doi.org/

Quotes from this episode:

"... (the amount) of uncertainty you're willing to deal with, and how much imprecision you're willing to deal with really drives your sample

Episode music: Shapeshifter by Mr Smith is licensed under a Attribution 4.0 International License. https://creativecommons.org/licenses/by/4.0/

https://freemusicarchive.org/music/mr-smith/studio-city/shapeshifter/

Cite this episode: https://doi.org/10.7944/usfws.wbtn.s01ep03

Citation formatter: https://citation.doi.org/

Previous Episode

Random Sampling Challenges and Examples

Delving into the significance of random sampling, hosts Matt, Grant, and Randy, use real-world examples to illustrate challenges associated with sampling, stressing the importance of random sampling for accurate representations of wildlife populations.

Episode quotes

"...my question for the group is, do you think, they can actually achieve their objectives with a sample size of one, with one transect inside a particular city. Do you think they can achieve that at the city scale?"

" Inside that rectangle, they're placing, camera traps to monitor species richness across that gradient of habitat from the lowlands to the uplands."

"...so to bring this home from where we began (referring back to episode 1), we had a garden with tomatoes in it, and now we have a city with wildlife in it. And so the garden area is is akin to our city area, and our the number of tomatoes in the garden that we wanna know the number of is is a parallel to the wildlife we want to sample in that city."

Episode music: Shapeshifter by Mr Smith is licensed under a Attribution 4.0 International License. https://creativecommons.org/licenses/by/4.0/

https://freemusicarchive.org/music/mr-smith/studio-city/shapeshifter/

Cite this episode: https://doi.org/10.7944/usfws.wbtn.s01ep02

Citation formatter: https://citation.doi.org/

Next Episode

Determining appropriate sample sizes to balance accuracy, precision, and resource allocation in wildlife studies

In this episode of Wildlife by the Numbers, Grant, Matt, and Randy, delve into the importance of proper sample size in wildlife studies. They emphasize that an adequate sample size is crucial for obtaining accurate and precise data, which directly impacts the reliability of conservation efforts. Sample size ensures representativeness and precision, critical for drawing valid conclusions about wildlife populations.

Matt explains that without a reasonable sample size, it is impossible to obtain a representative sample, leading to inaccurate estimations. The conversation touches on how over- or under-sampling can lead to either wasted resources or insufficient data, respectively. Randy discusses the challenges in achieving desired precision in various wildlife surveys, such as those involving fish in reservoirs, where spatial variability can complicate sampling.

Overall, this episode underscores the necessity of determining appropriate sample sizes to balance accuracy, precision, and resource allocation in wildlife studies, ensuring that conservation and management strategies are based on robust scientific data.

Episode Quotes:

"...the two issues that are intertwined in in sample size. One is representativeness, which we've talked about already,

and then the other is precision. Basically, how good is my estimate of that mean?"

"So as a wildlife biologist, getting the right sample size is important because it'll also help you get good results. And it also makes sure that the effort you put out is commensurate with the with the precision of the results you want. So you're not under sampling and spending a

lot of money and time and not getting a precise answer, and you're not oversampling by spending a lot of money and time and getting a really tight answer that you really don't need."

"...but I do know what they're aiming for. And, typically, they partition it based on whether or not it's gonna be a management or a research question. With the research question aiming for a CV of ten to fifteen percent and then a management based question, a CV of twenty to twenty five percent is is acceptable."

Episode music: Shapeshifter by Mr Smith is licensed under a Attribution 4.0 International License. https://creativecommons.org/licenses/by/4.0/

https://freemusicarchive.org/music/mr-smith/studio-city/shapeshifter/

Cite this episode: https://doi.org/10.7944/usfws.wbtn.s01ep04

DOI Citation Formatter: https://citation.doi.org/