Although ‘accurate’ and ‘precise’ are used interchangeably in day-to-day conversation, they mean different things in science. In science, an ‘accurate’ measurement is close to the actual or true value. For example, if I measure a 5 inch piece of string twice and get 5.1 and 4.8 inches as its length, the first measurement (5.1 inches) is more accurate. That’s because this measurement is closer to the true value.

In general, an aerosol is defined as several small particles of liquid or fine solid that are suspended in the air. When we’re talking about diseases, the distinction gets a bit finer. A disease is classified as being ‘air-transmissible’ if there is data showing that people can catch the disease by breathing in aerosols- fine, airborne infectious particles. The specific size of these small particles is up to debate, although below 5 uM in size is a commonly accepted benchmark. (Source)

For more on aerosols, check out this post where we summarize an article on air transmission of SARS-CoV-2.

An antigen is something that triggers an immune response- it’s the piece of enemy uniform that your immune cells recognize and mobilize against. Antigens are used to make vaccines. In a vaccine, an antigen is introduced to the body in a controlled way to train your immune response. Most SARS-CoV-2 vaccines use the spike protein, which is a strong SARS-CoV-2 antigen. For more on this, check out this sidebar.

“Antigen presenting cells” is often written as just “APCs.” APCs are a category of immune cells that display pieces of invading viruses or bacteria on their outer surface for other immune cells (like T cells) to recognize and leap into action. You can think of an antigen presenting cell as a scout. When one of these cells finds an enemy bacteria or virus, either by engulfing and killing it or by being infected by it, it takes a piece of that enemy back to ‘base’ to wake up and activate the soldiers. For more on this, check out Deanna’s sidebar! (Additional source)

In research, an assay is a technique or experimental procedure that is used to measure something about a sample. Assays can give you qualitative (yes/no) or quantitative (specific numerical measurement) answers about a sample. Types of assays include PCR, ELISA and Viral Plaque Assays.

If a person is asymptomatic, they don’t show any symptoms of a disease even though they are infected with it. Asymptomatic people can still spread the disease, so don’t assume that just because you’re feeling okay you’re good to go out into crowds! Keep your distance!

In science, bias is defined as any deviation from the true data. This can happen in data collection, interpretation of results or in how the results are presented. Bias can happen either intentionally or unintentionally. Blinded experiments are one tool scientists can use to avoid unintentional bias. Many research publications require that papers include a ‘conflict of interest’ section, which can also offer a window into potential sources of bias. For more about bias, check out this article.

A case study is a type of research method that looks at a single person, group or other unit in-depth. For example, this post summarizes a research paper that tracks a COVID19 outbreak in a single nursing unit. Since this study very closely follows nurses in that one unit and is dedicated to understanding how COVID19 spread through that unit (rather than conducting experiments), this is a case study.

A clinical study is done on human volunteers in a medical setting. Clinical studies can either be trials, which test new drugs and treatments, or observational studies, which just observe people in normal situations. Clinical trials come after pre-clinical trials, which are conducted on animal or cell models. (Source)

In a scientific experiment, the control group is the group that is left ‘untreated.’ Now what does that mean? Let’s use an example:

Say we want to know how UV light exposure affects the growth rate of bacterial cells. To do this experiment, we need a ‘baseline’ group, a set of bacterial cells that are left alone to grow like they normally would. We then compare the growth rate in this baseline group to the growth rate in a group of cells that received UV light treatment. The baseline, unexposed group is our control group. (Source)

A controlled experiment is run so that only a few variables are changed at a time. This helps us know which variable is causing any changes that are observed. To explain this, let’s continue the example from above:

In order to make the UV light/bacterial growth experiment  a properly controlled experiment, we have to make sure that the only difference between our control group (no UV treatment) and our experimental group (UV treated) is the exposure to UV light. To make sure that there’s no other differences, we have to control all the other variables. We can do this by:

• Using the same bacterial species and strain in both cases
• Growing the bacteria at the same temperature and humidity
• Growing the bacteria with the same type of nutrient
• Exposing the bacteria to the same wavelength of UV light for the same amount of time in each trial
• Measuring the growth rate in the same way

If an experiment isn’t fully controlled, we don’t have any way of knowing what caused any changes that we see. For example: if we didn’t use the same nutrient source, we wouldn’t know if the change in growth rate was because of the UV exposure or because one nutrient source is better than the other! Carefully controlled experiments are the bread and butter of scientific research, and they’re what distinguishes genuine scientific discoveries from impressions drawn from personal experience. I could say that I’ve never gotten a sunburn on the days I drink lemonade, but that observation is not based on a controlled experiment. The lemonade could have prevented a sunburn. On the other hand, I could have avoided getting a sunburn because I was sitting under an umbrella, or because I stayed inside or because I have a higher melanin content in my skin. There are too many uncontrolled variables!

In life science research, “culturing” cells means growing them in a lab environment, usually in a specific nutrient mix. When a paper says that something “grew readily in culture,” they mean that they were able to keep those cells or tissues alive and dividing in a lab environment. Tissue culture is one of the main things you have to do in a life science lab- keeping cells alive takes a lot of work!