In chinese, it called 家居服，means it's only for home.

In here, change means 换

在家里is prep.+n.  在is prep. 

In China, we like to feel comfortable and casual at home, if we intend to stay at home whole day, sometimes or some penple like to dress 家居服 all of day, but not everyone do it like this. Got it?

家居服 VS 睡衣

我有几个问题。人睡觉前应该换衣服吗? 例如,他们的家居服从早上穿到晚上（在家里, 不外出），然后不脱衣服。她们穿家居服睡觉，不穿睡衣，这是正常的吗？这经常发生在中国家庭吗？人每天应该换几次衣服?

我等待你们的答复和更正。谢谢大家。

I have few questions. Should people change their clothes before sleeping? For example, they wearing home clothes from the morning till evening (i mean, this clothes only for home, not for outside), after that they don't undress. Going to sleep in home clothes, not in pajamas. Is it normal? Is it often happen in Chinese families? How many times per day people should change their clothes?

I'm waiting your answers and corrections. Thanks to all.