与“a bit” 和 “a little”的可互换使用不同，"not a bit"与”not a little"有某些语境下意思可能完全相反。
1. not a bit 作状语时意思是“一点儿也不”, 相当于not……at all
I'm really not a bit surprised
我真的一点儿也不觉得惊讶。
After taking two hours' walk, he was not a bit tired.
走了两个小时以后，他一点都不觉得累。
She's not a bit interested in that topic.
她对那个话题一点都不感兴趣。
类似用法的词组：
in the least和in the slightest等。
I'm not in the least bit touched by the Marilyn Monroe kind of beauty
我对玛丽莲·梦露那种美一点儿都不动心。
He didn't seem in the least concerned for her safety.
对她的安全他似乎一点都不担心。
Her sudden appearance did not seem to perturb him in the least.
她的突然出现似乎一点也没有令他不安。
I don't think you need to worry in the least.
我看你一点也不用着急。
We were not in the least worried about the possibility that sweets could rot the teeth
我们以前完全不担心吃糖果有可能会蛀牙。
'Do you worry about ageing?' — 'Not in the slightest.'
“你担心变老吗？”——“一点也不。”
He didn't seem to mind in the slightest.
他好像一点都不在乎。
That doesn't interest me in the slightest
那一点也不能引起我的兴趣。
She doesn't like that man in the slightest.
她一点儿都不喜欢那个男人。
2. 但是not a little作状语时意思时，它可以被解释为“非常（多）地”，意味着某种程度上的强调，相当于“much”或“a lot”。一般not a little放到句尾修饰谓语动词时，含义就是“非常（多）地”：
I don’t love you a little.
我很爱你。
She was not a little worried about the expense.
她对那笔开支相当苦恼。
She was not a little pleased when she received the award.
她收到奖时非常高兴。
He was not a little surprised by her sudden decision.
他对她突然的决定感到非常吃惊。
He was surprised by her sudden decision not a little.
他对她突然的决定感到非常吃惊。
与a little 在否定句的用法相类似的词还有：slightly；试比较：
They didn’t praise her slightly.
他们对她大加赞扬。
They didn’t praise her in the slightest.
他们一点也没有赞扬她。