People's beliefs are based on past experience, but not always on fact. Have you ever expected someone to act a certain way based on your prior experience with her - then said, "Ah ha!" when you saw an example of that behavior? That is an example of confirmation bias, the human propensity for finding ways of upholding an existing hypothesis - and it's not a good thing. As a homeschool teacher, you must be aware of your own tendency for only presenting information that agrees with your preconceived notions. This is a particular danger when it comes to teaching science.
There are many ways that confirmation basis can negatively affect our thoughts and our lives. Just like racial bias toward a particular category of people, confirmation bias toward data can cause you to shy away from particular concepts or freely embrace the wrong information. It leads you to search out only the information that upholds your beliefs and shun conflicting information because it doesn't fit into your belief system.
We see evidence of this in the news all the time, especially around election season. Those who favor one political front runner over the other will eagerly grasp onto any favorable information regarding their chosen candidate while refuting - or even attempting to hide - denigrating facts. You will also do the opposite - gleefully sharing anything that makes the other guy look bad.
It comes to play in confirming our superstitions, too. Let's say you believe that walking down the sidewalk backwards at noon on Wednesday brings you good luck. While doing so, you see a black cat that decides to cross the street rather than cross your path. Then you spy a piece of paper wedged into the crack of the sidewalk and you pick it up only to find it's actually a hundred dollar bill. Even though you may have gotten drenched by a passing truck driving through a puddle and missed an important appointment because it took you too long to get there, your mind will focus only on the good things that happened because it confirms your belief that walking backwards is positive.
In terms of teaching, confirmation bias can easily slip into any day's agenda but especially during science lessons.
One way this is often evidenced is through the curriculum homeschool parents choose. If they describe themselves as Christians, they will choose only science textbooks that uphold their Creationism views. On the other hand, secular homeschoolers tend to seek out science resources that focus strictly on facts and often present Darwinism and the Big Bang theory to their kids.
While there's nothing wrong with any of those views, it could be a disservice to your kids to present only those views. Because of confirmation bias, which leads parents to actively seek out and teach only scientific facts that uphold their personal views, many parents deny a full, well-rounded education to their children. This can be especially confusing for kids who can easily find differing opinions online and through other resources. How will you explain the Big Bang theory to kids who have only been taught that God created all things in the universe?
Rather than have to try to explain it away, it might be best to present both scientific worldviews and show how both of them can fit into a Christian, creationistic worldview. Kids are smart. They know how to discover and explore the facts that may be eluding them and preventing real, deep understanding of scientific topics.
There's no need to be afraid of information because it is just that: information. Don't let your personal confirmation bias prevent your child from getting a whole education. As a homeschool science teacher, it's your job to give them all the information they ask for without fear and help them investigate it further.