Vehicular vs positive vs negative control

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lotus0618
Posts: 182
Joined: Sun Dec 29, 2019 5:47 pm

Vehicular vs positive vs negative control

Post by lotus0618 » Thu Jul 09, 2020 10:41 pm

How to test the impact of washing hands on the number of bacteria on sterilized spheres? the positive control is a sphere not being handled (= touched). How is this a positive control? Shouldn't this be a negative control, since the definition of the negative control is not adding a treatment (which is washing hands) or changing the treatment in a way that it would result in no responses? I thought a positive control in this situation would be washing our hands with some 'fake' soap and then handle the sphere to count the bacteria on the sphere later.

Also, how is a vehicular control different from negative control?

Can you please give me an example and point out the 3 types of control in the example? thanks

Please make it simple for me. I'm having a hard time with this. Thanks a lot
NS_Tutor_Yuqi
Posts: 53
Joined: Fri May 29, 2020 11:43 pm

Re: Vehicular vs positive vs negative control

Post by NS_Tutor_Yuqi » Sun Jul 12, 2020 1:40 pm

Unless there is more context information that is needed to answer this question, then you're right that a sphere not being handled would not be a positive control. Where did you find this question?

A vehicular control is a type of negative control, where you're controlling for the effects of the method of delivery of the treatment. This is usually discussed in the context of the placebo effect. Therefore, if someone is trying to test whether an orally administered drug is effective, the vehicular control would be administering a sugar pill to test whether the effects seen are due to the drug itself or the act of taking a pill. In this circumstance, a positive control would be administration of another drug that is known to have the same effect as the experimental drug. If this is successful, then it shows that your protocol and experimental set up are working as intended.
lotus0618
Posts: 182
Joined: Sun Dec 29, 2019 5:47 pm

Re: Vehicular vs positive vs negative control

Post by lotus0618 » Sun Jul 12, 2020 7:04 pm

The question is in the pre-made anki set. I don't understand why the sphere not being handled is a positive control? Can you please re-read my original post? It includes my confusion about this positive control.

In regard to your example, your positive control makes perfect sense to me because here the researchers administered another drug to the participants. Now for me in this situation, a negative control (in addition to your vehicular control) is not giving the patients any drugs, including no placebo drugs either. Is that correct?
lotus0618
Posts: 182
Joined: Sun Dec 29, 2019 5:47 pm

Re: Vehicular vs positive vs negative control

Post by lotus0618 » Thu Jul 16, 2020 2:45 pm

Please let me know. Thanks!
NS_Tutor_Yuqi
Posts: 53
Joined: Fri May 29, 2020 11:43 pm

Re: Vehicular vs positive vs negative control

Post by NS_Tutor_Yuqi » Sun Jul 19, 2020 1:49 pm

I think I might be getting confused about the experimental setup. Is the experiment measuring the amount of bacteria on the hands or on the spheres? What are they trying to test for?

You're technically correct about the negative control, although most experiments would not do that since they want to test for the placebo effect. That is why a vehicular control is so often used as a negative control.
lotus0618
Posts: 182
Joined: Sun Dec 29, 2019 5:47 pm

Re: Vehicular vs positive vs negative control

Post by lotus0618 » Sun Jul 19, 2020 2:32 pm

I'm sorry for the confusion.
It is "How to test the impact of washing hands on the number of bacteria on sterilized spheres? " So basically, they will test the number of bacteria on sterilized spheres after the participants wash their hands (or don't wash their hands with soap, or other ways depending on the type of control) and then touch the sterilized spheres
NS_Tutor_Yuqi
Posts: 53
Joined: Fri May 29, 2020 11:43 pm

Re: Vehicular vs positive vs negative control

Post by NS_Tutor_Yuqi » Sun Jul 26, 2020 2:55 pm

I think this Anki card is wrong since not touching sterilized spheres would theoretically result in a bacteria count of zero. In this situation, it would serve as the negative control, not the positive control
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